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low cost, high speed differential amplifier ad8132 rev. d in fo rmation furn ished by an alog d e v i c e s is believed to be accurate and reliable. how e ver, n o resp on sibili ty is assume d b y a n alog de vices fo r its use, nor for an y i n fri n geme nt s of p a t e nt s or ot h e r ri ght s o f th ird parties th at may result fro m its use . s p ecificatio n s subj ec t to ch an g e witho u t n o tice. no licen s e is g r an te d by implicati o n or ot herwi s e u n der a n y p a t e nt or p a t e nt ri ghts of analog de v i ces. trademarks an d registered tra d ema r ks are the prop erty o f their respective ow ners. one technolog y way, p.o . box 9106, norwood, ma 02062-9106, u.s.a. t e l: 781. 329. 4 700 www.analog.com fax: 781. 326. 87 03 ? 2004 analog de vices, i n c. al l r i ght s r e ser v ed . fea t ures high speed 350 mh z ? 3 db bandwidth 1200 v/s slew rate resistor settab l e gain internal common-mode feed back to improve gain and phase balance ?68 db @ 1 0 m hz separate input to set the common-mode output voltage low distortion: ?99 dbc sfdr @ 5 m hz 8 00 ? load low power: 10.7 ma @ 5 v po wer supply r a nge: +2.7 v to 5.5 v applic a t io ns low power diff erential adc dr ivers differentia l gai n and di fferent ial filt ering video line dri v ers differentia l in/ o ut leve l shifti ng single-ended i n put to differential output dri v ers active trans f ormers gener a l description the ad8132 is a lo w cos t dif f er en t i al o r sin g le-en d ed in p u t t o dif f er en t i a l ou t p u t a m plif ier wi t h r e sist o r s e t t a b le ga in. t h e ad8132 is a ma jo r ad van c em en t o v er o p a m ps f o r dr i v in g dif f er en tial in p u t ad cs o r fo r dr i v in g sig n als o v er lo n g lin e s. the ad8132 has a uniq ue in t e r n al f eed b a c k f e a t ur e tha t p r o v ides o u tp u t ga in and phas e ma tch i n g b a lance d to ?68 db a t 10 mh z, s u p p r es sin g ha r m onic s a nd r e d u cin g radia t ed emi. m a n u fac t ur e d usin g ad i s n e xt g e n e r a tio n xfc b b i p o la r p r o c es s, th e ad8132 has a ?3 db ba ndwid th o f 350 mh z and de li v e rs a dif f er en t i al sig n al wi t h ?99 db c s f dr a t 5 m h z, des p i t e i t s lo w cos t . the ad813 2 e l imina t es t h e n e e d f o r a t r a n sfo r m e r wi t h hig h p e r f o r ma n c e a d cs, p r e s er vin g t h e lo w f r e q uen c y a nd dc info r m a t io n. the co m m on- m o d e le vel o f t h e dif f er en t i a l ou t p u t is ad j u st ab le b y a p ply i n g a vol t a g e on t h e v oc m p i n, e a sil y le v e l shif ting the in p u t sig n als fo r dr i v in g sin g le-s up pl y a d cs. f a s t o v erlo ad r e co v e r y p r es er v e s s a m p ling acc u rac y . func ti on a l bl ock di a g r a m ?in 1 v ocm 2 v+ 3 +out 4 +in 8 nc 7 v? 6 ?out 5 nc = no connect ad8132 01035-001 fi g u r e 1 . the ad8132 can als o be us e d as a dif f er en t i al dr i v er f o r th e tra n smis sio n o f hig h sp e e d sig n als o v er l o w cos t twis te d p a ir o r coa x i a l ca b l e s . th e f e e d ba ck n e tw o r k ca n be ad j u s t ed t o boos t th e hig h f r eq uen c y co m p on en ts o f th e sig n al . the ad8132 can b e u s e d f o r e i t h e r an a l o g or d i g i t a l v i d e o s i g n a l s or f o r ot he r hig h sp ee d da ta tra n smis sio n . th e ad8132 is ca p a b l e o f dr i v in g ei t h er ca t3 o r ca t5 t w iste d p a ir or co axia l w i t h minima l li n e a t t e n u a t io n. the ad8132 has c o n s idera b le cos t a nd p e r f o r ma n c e im p r o v em en t s o v er dis c r e t e li n e dr i v er s o l u t i o n s. dif f er en t i al sig n al p r o c es sin g re d u ces t h e ef fe c t s o f g r o u n d n o is e tha t pla g u e s g r o u n d r e f e r e n c e d sys t em s. th e ad8132 ca n b e us e d fo r dif f er en t i al sig n al p r o c es sin g (ga i n and f i l t er in g) thr o ug h o u t a sig n al c h a i n, e a sily sim p lif y in g t h e co n v ersion bet w een d i f f e r en tial a n d s i n g l e -e n d ed co m p o n en t s . the ad8132 is a v a i la b l e in bo t h so i c and ms o p p a c k a g es f o r o p era t ion o v er ?40c t o +125c t e m p era t ur es. frequency (mhz) 6 1 gain ( d b) 3 0 ?3 ?6 ?9 ?12 10 100 1k v s = 5v g = +1 v o, dm = 2v p-p r l, dm = 499 ? 01035-002 fi g u r e 2 . l a r g e s i g n a l fr e q u e n c y r e s p o n s e
ad8132 rev. d | page 2 of 32 table of contents specifications..................................................................................... 3 d in to out specifications...................................................... 3 v ocm to out specifications ..................................................... 4 d in to out specifications...................................................... 5 v ocm to out specifications ..................................................... 6 d in to out specifications...................................................... 7 v ocm to out specifications ..................................................... 7 absolute maximum ratings............................................................ 8 esd caution.................................................................................. 8 pin configuration and function descriptions............................. 9 typical performance characteristics ........................................... 10 test circuits..................................................................................... 19 operational description................................................................ 20 definition of terms.................................................................... 20 basic circuit operation ............................................................. 20 theory of operation ...................................................................... 21 general usage of the ad8132................................................... 21 resistorless differential amplifier (high input impedance inverting amplifier)................................................................... 21 other 2 = 1 circuits ................................................................. 22 varying 2 ................................................................................... 22 1 = 0............................................................................................ 22 estimating the output noise voltage ...................................... 22 calculating an application circuits input impedance ......... 23 input common-mode voltage range in single-supply applications ................................................................................ 23 setting the output common-mode voltage .......................... 23 driving a capacitive load......................................................... 23 layout, grounding, and bypassing .............................................. 24 circuits......................................................................................... 24 applications..................................................................................... 25 a/d driver .................................................................................. 25 balanced cable driver............................................................... 25 transmit equalizer ..................................................................... 26 low-pass differential filter ...................................................... 26 high common-mode output impedance amplifier............ 27 full-wave rectifier .................................................................... 27 outline dimensions ....................................................................... 29 ordering guide .......................................................................... 29 revision history 12/04rev. c to rev. d. changes to the general description.............................................. 1 changes to the specifications ......................................................... 2 changes to the absolute maximum ratings................................. 8 updated the outline dimensions................................................. 29 changes to the ordering guide.................................................... 29 2/03rev. b to rev. c. changes to specifications .......................................................2 addition to estimating the output noise voltage section ....... 15 updated outline dimensions ............................................ 21 1/02rev. a to rev. b. edits to transmitter equalizer section ...........................18
ad8132 rev. d | page 3 of 32 specifications d in to out specifications at 25c, v s = 5 v, v ocm = 0 v, g = 1, r l, dm = 499 ?, r f = r g = 348 ?, unless otherwise noted. for g = 2, r l, dm = 200 ?, r f = 1000 ?, r g = 499 ?. refer to figure 56 and figure 57 for test setup and label descriptions. all specifications refer to single-ended inpu t and differential outputs, unless otherwise noted. table 1. parameter conditions min typ max unit dynamic performance ?3 db large signal bandwidth v out = 2 v p-p 300 350 mhz v out = 2 v p-p, g = 2 190 mhz ?3 db small signal bandwidth v out = 0.2 v p-p 360 mhz v out = 0.2 v p-p, g = 2 160 mhz bandwidth for 0.1 db flatness v out = 0.2 v p-p 90 mhz v out = 0.2 v p-p, g = 2 50 mhz slew rate v out = 2 v p-p 1000 1200 v/s settling time 0.1%, v out = 2 v p-p 15 ns overdrive recovery time v in = 5 v to 0 v step, g = 2 5 ns noise/harmonic performance second harmonic v out = 2 v p-p, 1 mhz, r l, dm = 800 ? ?96 dbc v out = 2 v p-p, 5 mhz, r l, dm = 800 ? ?83 dbc v out = 2 v p-p, 20 mhz, r l, dm = 800 ? ?73 dbc third harmonic v out = 2 v p-p, 1 mhz, r l, dm = 800 ? ?102 dbc v out = 2 v p-p, 5 mhz, r l, dm = 800 ? ?98 dbc v out = 2 v p-p, 20 mhz, r l, dm = 800 ? ?67 dbc imd 20 mhz, r l, dm = 800 ? ?76 dbc ip3 20 mhz, r l, dm = 800 ? 40 dbm input voltage noise (rti) f = 0.1 mhz to 100 mhz 8 nv/ hz input current noise f = 0.1 mhz to 100 mhz 1.8 pa/ hz differential gain error ntsc, g = 2, r l, dm = 150 ? 0.01 % differential phase error ntsc, g = 2, r l, dm = 150 ? 0.10 degrees input characteristics offset voltage (rti) v os, dm = v out, dm /2; v din+ = v din? = v ocm = 0 v 1.0 3.5 mv t min to t max variation 10 v/c input bias current 3 7 a input resistance differential 12 m? common-mode 3.5 m? input capacitance 1 pf input common-mode voltage ?4 to +3 v cmrr ?v out, dm /?v in, cm ; ?v in, cm = 1 v; resistors matched to 0.01% ?70 ?60 db output characteristics output voltage swing maximum ?v out ; single-ended output ?3.6 to +3.6 v output current 70 ma output balance error ?v out, cm /?v out, dm ; ?v out, dm = 1 v ?70 db
ad8132 rev. d | page 4 of 32 v ocm to out specifications at 25c, v s = 5 v, v ocm = 0 v, g = 1, r l, dm = 499 ?, r f = r g = 348 ?, unless otherwise noted. for g = 2, r l, dm = 200 ?, r f = 1000 ?, r g = 499 ?. refer to figure 56 and figure 57 for test setup and label descriptions. all specifications refer to single-ended inpu t and differential outputs, unless otherwise noted. table 2. parameter conditions min typ max unit dynamic performance ?3 db bandwidth ?v ocm = 600 mv p-p 210 mhz slew rate ?v ocm = ?1 v to +1 v 400 v/s input voltage noise (rti) f = 0.1 mhz to 100 mhz 12 nv/ hz dc performance input voltage range 3.6 v input resistance 50 k? input offset voltage v os, cm = v out, cm ; v din+ = v din? = v ocm = 0 v 1.5 7 mv input bias current 0.5 a v ocm cmrr ?v out, dm /?v ocm ; ?v ocm = 1 v; resistors matched to 0.01% ?68 db gain ?v out, cm /?v ocm ; ?v ocm = 1 v 0.985 1 1.015 v/v power supply operating range 1.35 5.5 v quiescent current v din+ = v din? = v ocm = 0 v 11 12 13 ma t min to t max variation 16 a/c power supply rejection ratio ?v out, dm /?v s ; ?v s = 1 v ?70 ?60 db operating temperature range ?40 +125 c
ad8132 rev. d | page 5 of 32 d in to out specifications at 25c, v s = 5 v, v ocm = 2.5 v, g = 1, r l, dm = 499 ?, r f = r g = 348 ?, unless otherwise noted. for g = 2, r l, dm = 200 ?, r f = 1000 ?, r g = 499 ?. refer to figure 56 and figure 57 for test setup and label descriptions. all specifications refer to single-ended inpu t and differential outputs, unless otherwise noted. table 3. parameter conditions min typ max unit dynamic performance ?3 db large signal bandwidth v out = 2 v p-p 250 300 mhz v out = 2 v p-p, g = 2 180 mhz ?3 db small signal bandwidth v out = 0.2 v p-p 360 mhz v out = 0.2 v p-p, g = 2 155 mhz bandwidth for 0.1 db flatness v out = 0.2 v p-p 65 mhz v out = 0.2 v p-p, g = 2 50 mhz slew rate v out = 2 v p-p 800 1000 v/s settling time 0.1%, v out = 2 v p-p 20 ns overdrive recovery time v in = 2.5 v to 0 v step, g = 2 5 ns noise/harmonic performance second harmonic v out = 2 v p-p, 1 mhz, r l, dm = 800 ? ?97 dbc v out = 2 v p-p, 5 mhz, r l, dm = 800 ? ?100 dbc v out = 2 v p-p, 20 mhz, r l, dm = 800 ? ?74 dbc third harmonic v out = 2 v p-p, 1 mhz, r l, dm = 800 ? ?100 dbc v out = 2 v p-p, 5 mhz, r l, dm = 800 ? ?99 dbc v out = 2 v p-p, 20 mhz, r l, dm = 800 ? ?67 dbc imd 20 mhz, r l, dm = 800 ? ?76 dbc ip3 20 mhz, r l, dm = 800 ? 40 dbm input voltage noise (rti) f = 0.1 mhz to 100 mhz 8 nv/ hz input current noise f = 0.1 mhz to 100 mhz 1.8 pa/ hz differential gain error ntsc, g = 2, r l, dm = 150 ? 0.025 % differential phase error ntsc, g = 2, r l, dm = 150 ? 0.15 degree input characteristics offset voltage (rti) v os, dm = v out, dm /2; v din+ = v din? = v ocm = 2.5 v 1.0 3.5 mv t min to t max variation 6 v/c input bias current 3 7 a input resistance differential 10 m? common-mode 3 m? input capacitance 1 pf input common-mode voltage 1 to 3 v cmrr ?v out, dm /?v in, cm ; ?v in, cm = 1 v; resistors matched to 0.01% ?70 ?60 db output characteristics output voltage swing maximum ?v out ; single-ended output 1.0 to 4.0 v output current 50 ma output balance error ?v out, cm /?v out, dm ; ?v out, dm = 1 v ?68 db
ad8132 rev. d | page 6 of 32 v ocm to out specifications at 25c, v s = 5 v, v ocm = 2.5 v, g = 1, r l, dm = 499 ?, r f = r g = 348 ?, unless otherwise noted. for g = 2, r l, dm = 200 ?, r f = 1000 ?, r g = 499 ?. refer to figure 56 and figure 57 for test setup and label descriptions. all specifications refer to single-ended inpu t and differential outputs, unless otherwise noted. table 4. parameter conditions min typ max unit dynamic performance ?3 db bandwidth ?v ocm = 600 mv p-p 210 mhz slew rate ?v ocm = 1.5 v to 3.5 v 340 v/s input voltage noise (rti) f = 0.1 mhz to 100 mhz 12 nv/ hz dc performance input voltage range 1.0 to 3.7 v input resistance 30 k? input offset voltage v os, cm = v out, cm ; v din+ = v din? = v ocm = 2.5 v 5 11 mv input bias current 0.5 a v ocm cmrr ?v out, dm /?v ocm ; ?v ocm = 2.5 v 1 v; resistors matched to 0.01% ?66 db gain ?v out, cm /?v ocm ; ?v ocm = 2.5 v 1 v 0.985 1 1.015 v/v power supply operating range 2.7 11 v quiescent current v din+ = v din? = v ocm = 2.5 v 9.4 10.7 12 ma t min to t max variation 10 a/c power supply rejection ratio ?v out, dm /?v s ; ?v s = 1 v ?70 ?60 db operating temperature range ?40 +125 c
ad8132 rev. d | page 7 of 32 d in to out specifications at 25c, v s = 3 v, v ocm = 1.5 v, g = 1, r l, dm = 499 ?, r f = r g = 348 ? unless otherwise noted. for g = 2, r l, dm = 200 ?, r f = 1000 ?, r g = 499 ?. refer to figure 56 and figure 57 for test setup and label descriptions. all specifications refer to single-ended inpu t and differential outputs, unless otherwise noted. table 5. parameter conditions min typ max unit dynamic performance ?3 db large signal bandwidth v out = 1 v p-p 350 mhz v out = 1 v p-p, g = 2 165 mhz ?3 db small signal bandwidth v out = 0.2 v p-p 350 mhz v out = 0.2 v p-p, g = 2 150 mhz bandwidth for 0.1 db flatness v out = 0.2 v p-p 45 mhz v out = 0.2 v p-p, g = 2 50 mhz noise/harmonic performance second harmonic v out = 1 v p-p, 1 mhz, r l, dm = 800 ? ?100 dbc v out = 1 v p-p, 5 mhz, r l, dm = 800 ? ?94 dbc v out = 1 v p-p, 20 mhz, r l, dm = 800 ? ?77 dbc third harmonic v out = 1 v p-p, 1 mhz, r l, dm = 800 ? ?90 dbc v out = 1 v p-p, 5 mhz, r l, dm = 800 ? ?85 dbc v out = 1 v p-p, 20 mhz, r l, dm = 800 ? ?66 dbc input characteristics offset voltage (rti) v os, dm = v out, dm /2; v din+ = v din? = v ocm = 1.5 v 10 mv input bias current 3 a cmrr ?v out, dm /?v in, cm ; ?v in, cm = 0.5 v; resistors matched to 0.01% ?60 db v ocm to out specifications at 25c, v s = 3 v, v ocm = 1.5 v, g = 1, r l, dm = 499 ?, r f = r g = 348 ? unless otherwise noted. for g = 2, r l, dm = 200 ?, r f = 1000 ?, r g = 499 ?. refer to figure 56 and figure 57 for test setup and label descriptions. all specifications refer to single-ended inpu t and differential outputs, unless otherwise noted. table 6. parameter conditions min typ max unit dc performance input offset voltage v os, cm = v out, cm ; v din+ = v din? = v ocm = 1.5 v 7 mv gain ?v out, cm /?v ocm ; ?v ocm = 0.5 v 1 v/v power supply operating range 2.7 11 v quiescent current v din+ = v din? = v ocm = 0 v 7.25 ma power supply rejection ratio ?v out, dm /?v s ; ?v s = 0.5 v ?70 db operating temperature range ?40 +125 c
ad8132 rev. d | page 8 of 32 absolute maximum ratings table 7. 1 p a r a m e t e r r a t i n g s supply voltage 5.5 v v ocm v s internal power dissipation 250 mw operating tem p erature range ?40c to +125c storage temperature range ?65c to +150c lead temperature (soldering 10 sec) 300c 1 th erm a l r e si st a n ce m e a s ur ed on s e m i - s t a n d a r d, 4- la yer boa r d. 8-lead soi c : ja = 1 21c/w 8-lead msop: ja = 142c/w s t r e s s es a b o v e t h os e lis t e d u n de r a b s o l u t e maxi m u m r a t i n g s ma y c a us e p e r m a n en t dama ge t o t h e de vice . this is a s t r e s s ra t i n g onl y ; f u n c t i o n al o p era t ion o f t h e de vice a t t h es e o r an y o t h e r con d i t io ns a b o v e t h os e list e d i n t h e o p era t io nal s e c t ion o f t h is sp e c if ic a t ion is n o t i m plie d . e x p o sur e t o a b s o l u t e m a x i m u m r a t i ng s for e x te nd e d p e r i o d s m a y a f fe c t d e v i c e rel i a b i l it y . ambient temperature ( c) ?50 0 t j = 150 c 2.0 1.5 1.0 m a xim u m pow e r d i ssipa tion ( w ) 8-lead soic package ?40 ? 30 0 1 0 2 03 0 4 0 5 0 6 07 0 8 0 9 0 8-lead msop package 0.5 ?20 ? 10 01035-003 f i g u re 3. p l ot of m a x i mum p o wer d i s s i pat i o n v s . t e mpe r a t ur e esd caution esd (electrostatic discharge) sensitive device. ele c tr ostatic charg e s as high as 4000 v readily accumulate on the human body and test eq uipment and can discharg e wit h out detection. althou gh this product features proprietary esd protection circu i try, permanent dama ge may occur on devices subjected to high energy electrostatic discharges. theref ore, prop er esd precautions a r e recommended to avoid perform a nce degradation or l o ss of functiona l ity.
ad8132 rev. d | page 9 of 32 pin conf iguration and fu nction descriptions ?in 1 v ocm 2 v+ 3 +out 4 +in 8 nc 7 v? 6 ?out 5 nc = no connect ad8132 01035-004 f i gure 4. pin config ur ation ta ble 8. pi n f u nct i on d e s c ri pt i o ns pin no . m n e m o n i c d e s c r i p t i o n 1 ? i n negative i n p u t . 2 v ocm voltage applied to this pin sets the common-mode output voltage with a ratio of 1:1. for example, 1 v dc on v ocm sets the d c bias le vel o n +o ut and ?out to 1 v. 3 v + positive supply v o l t a g e . 4 + o u t positive output. note that the v o ltage at ?d in is inverted at +out (see figure 64). 5 ? o u t negative outpu t . note that the voltage at +d in is inverted at ?out (see figure 64). 6 v? negative supply voltage. 7 n c no c o n n e c t . 8 + i n positive i n p u t .
ad8132 rev. d | page 10 of 32 typical perf orm ance cha r acte ristics 01035-006 frequency (mhz) gain ( d b) 2 1 1 0 ? 1 ? 2 ? 3 ? 4 ? 5 10 100 1k g = +1 v o, dm = 0.2v p-p r l, dm = 499 ? v s = +3v v s = +5v v s = 5v fi g u r e 5 . s m a l l s i g n a l fr e q u e n c y r e s p o n s e ( s e e fi g u r e 5 6 ) frequency (mhz) gain ( d b) 1 1 0 100 1k 0.4 0.3 0.2 0.1 0 ?0.1 ?0.2 ?0.3 ?0.4 ?0.5 0.5 g = +1 v o, dm = 0.2v p-p r l, dm = 499 ? v s = +3v v s = +5v v s = 5v 01035-007 f i g u re 6. 0.1 db f l at nes s v s . f r eque nc y c f = 0 pf (s e e f i gur e 56 ) frequency (mhz) gain ( d b) 1 1 0 100 1k g = +1 v o, dm = 0.2v p-p r l, dm = 499 ? 0.2 0.1 0 ?0.1 ?0.2 ?0.3 ?0.4 ?0.5 v s = +3v v s = +5v v s = 5v 01035-008 f i g u re 7. 0.1 db f l at nes s v s . f r eque nc y c f = 0. 5 pf (s e e f i g u r e 5 6 ) frequency (mhz) gain ( d b) 1 1 0 100 1k 2 1 0 ? 1 ? 2 ? 3 ? 4 ? 5 3 g = +1 v o, dm = 2v p-p for v s = 5v, +5v v o, dm = 1v p-p for v s = +3v r l, dm = 499 ? v s = +3v v s = +5v v s = 5v 01035-009 v s = +3v fi g u r e 8 . l a r g e s i g n a l fr e q u e n c y r e s p o n s e ; c f = 0 pf (s ee f i g u r e 56) frequency (mhz) gain ( d b) 1 1 0 100 1k 2 1 0 ?1 ?2 ?3 ?4 ?5 g = +1 v o, dm = 2v p-p for v s = 5v, +5v v o, dm = 1v p-p for v s = +3v r l, dm = 499 ? v s = +3v v s = +5v v s = 5v v s = +3v 01035-010 fi g u r e 9 . l a r g e s i g n a l fr e q u e n c y r e s p o n s e ; c f = 0.5 pf (s ee f i g u re 56) frequency (mhz) gain ( d b) 1 1 0 100 1k 2 1 0 ?1 ?2 ?3 ?4 ?5 3 v s = 5v g = +1 v o, dm = 2v p-p r l, dm = 499 ? ?40 c +85 c +25 c 01035-011 f i g u re 10. lar g e s i g n al r e s p ons e v s . t e mper at ur e (s e e f i g u r e 56)
ad8132 rev. d | page 11 of 32 frequency (mhz) gain ( d b) 1 1 0 100 1k 2 1 0 ?1 ?2 ?3 ?4 ?5 3 v s = 5v g = +1 v o, dm = 2v p-p r l, dm = 499 ? r f = 499 ? r f = 348 ? r f = 249 ? 01035-012 f i gure 1 1 . la r g e s i gna l f r equenc y r e sp o n se vs . r f (s e e f i g u r e 56) frequency (mhz) imp e dance ( ? ) 100 1 10 1 0.1 10 100 v s = +5v v s = 5v 01035-013 f i g u re 12. cl os ed-l oop sing le -e nd ed z ou t v s . f r equenc y ; g = 1 (s ee f i gu r e 5 6 ) frequency (mhz) gain ( d b) 7 1 6 5 4 3 2 1 10 100 1k g = +2 v o, dm = 0.2v p-p r l, dm = 200 ? v s = +3v v s = 5v, +5v 01035-015 fi g u r e 1 3 . s m a l l s i g n a l fr e q u e n c y r e s p o n s e ( s e e fi g u r e 5 7 ) frequency (mhz) gain ( d b) 1 1 0 100 1k v s = +3v, +5v, 5v g = +2 v o, dm = 0.2v p-p r l, dm = 200 ? 6.1 6.0 5.9 5.8 5.7 5.6 5.5 01035-016 f i g u re 14. 0. 1 db f l at nes s v s . f r equ e nc y (s ee f i g u r e 5 7 ) frequency (mhz) gain ( d b) 1 1 0 100 1k 7 6 5 4 3 2 1 v s = +5v, 5v v s = +3v g = +2 v o, dm = 2v p-p for v s = 5v, +5v v o, dm = 1v p-p for v s = +3v r l, dm = 200 ? 01035-017 f i gure 15. lar g e s i gnal f r equenc y r e sponse ( s ee f i gu r e 5 7 ) frequency (mhz) gain ( d b) 1 1 0 100 1k 7 6 5 4 3 2 1 v s = 5v g = +2 v o, dm = 0.2v p-p r l, dm = 200 ? r f = 1.0k ? r f = 499 ? r f = 1.5k ? 01035-018 f i gure 1 6 . smal l s i gna l f r equenc y r e sp o n se vs . r f (s e e f i g u r e 57)
ad8132 rev. d | page 12 of 32 frequency (mhz) gain ( d b) 1 1 0 100 1k 25 20 15 10 5 0 ?5 v s = 5v v o, dm = 2v p-p r l, dm = 200 ? r g = 499 ? ?1 0 ?1 5 g = +10, r f = 4.99k ? g = +5, r f = 2.49k ? g = +2, r f = 1k ? g = +1, r f = 499 ? 01035-020 f i gur e 1 7 . la r g e signa l r e sp o n se fo r v a r i o u s g a i n s ( s ee f i gur e 5 8 ) frequency (mhz) rti balance e rror (db) 1 1 0 100 1k ? 25 ?30 ?35 ?40 ?45 ?50 ?55 v s = 5v ? v o, dm = 2v p-p ? v o, cm / ? v o, dm ?60 ?65 g = +1 g = +2 ?70 ?75 01035-022 f i gure 18. rti o u tp ut bal a nce e r r o r v s . f r eq uenc y ( s ee f i g u r e 5 9 ) frequency (mhz) distortion ( d bc) 0 5 06 07 ?4 0 ?5 0 ?60 ?70 ?80 ?9 0 ?100 0 20 30 40 10 ?110 r l, dm = 800 ? v o, dm = 1v p-p hd3 (v s = 3v) hd2 (v s = 3v) hd2 (v s = 5v) hd3 (v s = 5v) 01035-024 f i g u re 19. h a r m o n i c d i s t o r t i o n v s . f r e q uenc y , g = 1 ( s e e f i g u re 62) frequency (mhz) distortion ( d bc) 05 ?40 ?50 ?60 ?70 ?80 ?90 ? 100 20 30 40 10 ? 110 0 6 0 7 0 r l, dm = 800 ? v o, dm = 2v p-p hd3 (v s = +5v) hd2 (v s = 5v) hd2 (v s = +5v) hd3 (v s = 5v) ?30 01035-025 f i g u re 20. h a r m o n i c d i s t o r t i o n v s . f r e q uenc y , g = 1 ( s e e f i g u re 62) differential output voltage (v p-p) distortion ( d bc) 0.25 1.50 1.75 ?40 ?50 ?60 ?70 ?80 ?90 ?100 0.75 1.00 1.25 0.50 ?110 v s = 3v r l, dm = 800 ? hd3 (f = 20mhz) hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 01035-026 f i gur e 2 1 . ha rm onic di stor ti on vs . d i f f e r e nt ia l o u t p ut v o lt ag e , g = 1 ( s e e f i g u r e 62) differential output voltage (v p-p) distortion ( d bc) 0 ? 40 ? 50 ? 60 ? 70 ? 80 ? 90 ? 100 23 1 ? 110 4 v s = 5v r l, dm = 800 ? hd3 (f = 20mhz) hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 01035-027 f i gur e 2 2 . ha rm onic di stor ti on vs . d i f f e r e nt ia l o u t p ut v o lt ag e , g = 1 ( s e e f i g u r e 62)
ad8132 rev. d | page 13 of 32 differential output voltage (v p-p) distortion ( d bc) 0 ?4 0 ?50 ?60 ?70 ?80 ?90 ? 100 23 4 1 ? 110 v s = 5v r l, dm = 800 ? hd3 (f = 20mhz) hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 5 6 01035-028 f i gur e 2 3 . ha rm onic di stor ti on vs . d i f f e r e nt ia l o u t p ut v o lt ag e , g = 1 ( s e e f i g u r e 62) r load ( ? ) distortion ( d bc) 200 700 800 ? 50 ? 60 ? 70 ? 80 ? 90 ? 100 400 500 600 300 ? 110 v s = 3v v o, dm = 1v p-p 900 1000 hd3 (f = 20mhz) hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 01035-029 f i gur e 2 4 . ha rm onic di stor ti on vs . r lo a d , g = 1 ( s ee f i g u r e 62) r load ( ? ) distortion ( d bc) 200 700 800 ? 50 ?60 ?70 ?80 ?90 ? 100 400 500 600 300 ? 110 v s = 5v v o, dm = 2v p-p 900 1000 hd3 (f = 20mhz) hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 01035-030 f i gur e 2 5 . ha rm onic di stor ti on vs . r lo a d , g = 1 ( s ee f i g u r e 62) r load ( ? ) distortion ( d bc) 200 700 800 ? 50 ? 60 ? 70 ? 80 ? 90 ? 100 400 500 600 300 ? 110 v s = 5v v o, dm = 2v p-p hd3 (f = 20mhz) hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 900 1000 01035-031 f i gur e 2 6 . ha rm onic di stor ti on vs . r lo a d , g = 1 ( s ee f i g u r e 62) frequency (mhz) distortion ( d bc) 40 50 ? 50 ? 60 ? 70 ? 80 ? 90 ? 100 10 20 30 0 ? 110 hd3 (v s = 3v) 60 70 r l,dm = 800 ? v o, dm = 1v p-p ? 40 hd3 (v s = 5v) hd2 (v s = 5v) hd2 (v s = 3v) 01035-033 f i g u re 27. h a r m o n i c d i s t o r t i o n v s . f r e q uenc y , g = 2 ( s e e f i g u re 63) frequency (mhz) distortion ( d bc) 40 50 ?50 ?60 ?70 ?80 ?90 ?100 10 20 30 0 hd3 (v s = 5v) 60 70 r l, dm = 800 ? v o,dm = 4v p-p ?40 hd3 (v s = +5v) hd2 (v s = +5v) 80 ?30 ?20 hd2 (v s = 5v) 01035-034 f i g u re 28. h a r m o n i c d i s t o r t i o n v s . f r e q uenc y , g = 2 ( s e e f i g u re 63)
ad8132 rev. d | page 14 of 32 differential output voltage (v p-p) distortion ( d bc) 2 ?5 0 ?6 0 ?7 0 ?8 0 ?9 0 ?100 1 03 v s = 5v r l, dm = 800 ? ? 40 hd3 (f = 20mhz) 4 ?110 ?120 hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 01035-035 f i gur e 2 9 . ha rm onic di stor ti on vs . d i f f e r e nt ia l o u t p ut v o lt ag e , g = 2 ( s e e f i g u r e 63) differential output voltage (v p-p) distortion ( d bc) 2 ?50 ?60 ?70 ?80 ?90 ? 100 1 03 v s = 5v r l, dm = 800 ? ?40 hd3 (f = 20mhz) 4 ? 110 hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 56 01035-036 f i gur e 3 0 . ha rm onic di stor ti on vs . d i f f e r e nt ia l o u t p ut v o lt ag e , g = 2 ( s e e f i g u r e 63) r load ( ? ) distortion ( d bc) 400 ?5 0 ?6 0 ?70 ?8 0 ?9 0 ? 100 300 200 500 hd3 (f = 20mhz) 600 ? 110 hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 700 800 v s = 5v v o, dm = 2v p-p 900 1000 01035-037 f i gur e 3 1 . ha rm onic di stor ti on vs . r lo a d , g = 2 ( s ee f i g u r e 63) r load ( ? ) distortion ( d bc) 400 ?5 0 ?6 0 ?7 0 ?8 0 ?9 0 ?100 300 200 500 hd3 (f = 20mhz) 600 ? 110 hd2 (f = 20mhz) hd2 (f = 5mhz) hd3 (f = 5mhz) 700 800 v s = 5v v o, dm = 2v p-p 900 1000 01035-038 f i gur e 3 2 . ha rm onic di stor ti on vs . r lo a d , g = 2 ( s ee f i g u r e 63) frequency (mhz) p out (dbm [re : 5 0 ? ]) 10 19.5 0 ?10 ?20 ?30 ?40 ?50 ?60 ?70 ?80 ?90 20.0 20.5 f c = 20mhz v s = 5v r l, dm = 800 ? 01035-039 f i gur e 3 3 . int e rm odul a t i o n di stor ti on, g = 1 frequency (mhz) 45 15 01 0 7 0 20 30 40 50 60 40 35 30 25 20 v s = 5v, +5v r l, dm = 800 ? intercept ( d bm [ r e: 50 ? ]) 01035-040 f i gure 34. thi r d- o r der in terc ept v s . f r e q uenc y , g = 1
ad8132 rev. d | page 15 of 32 01035-041 v s = 5v, +5v, +3v 40mv 5ns f i g u re 35. sm a ll s i g n al t r ans i ent r e s p ons e , g = 1 300mv 5ns v s = 3v v o, dm = 1.5v p-p c f = 0pf c f = 0.5pf 01035-042 f i g u re 36. lar g e s i g n al t r ans i ent r e s p ons e , g = 1 01035-043 400mv 5ns v s = 5v v o, dm = 2v p-p c f = 0pf c f = 0.5pf f i g u re 37. lar g e s i g n al t r ans i ent r e s p ons e , g = 1 01035-044 v s = 5v v o,dm = 2v p-p 400mv 5ns c f = 0pf c f = 0.5pf f i g u re 38. lar g e s i g n al t r ans i ent r e s p ons e , g = 1 01035-045 1v 5ns v ? out v +out v +din v o, dm f i g u re 39. lar g e s i g n al t r ans i ent r e s p ons e , g = 1 01035-046 40mv 5ns v s = 5v, +5v, +3v f i g u re 40. sm a ll s i g n al t r ans i ent r e s p ons e , g = 2
ad8132 rev. d | page 16 of 32 01035-047 300mv 5ns v s = 3v f i g u re 41. lar g e s i g n al t r ans i ent r e s p ons e , g = 2 01035-048 400mv 5ns v s = +5v, 5v f i g u re 42. lar g e s i g n al t r ans i ent r e s p ons e , g = 2 01035-049 1v 5ns v s = 5v v o, dm v ? out v +out v +din f i g u re 43. lar g e s i g n al t r ans i ent r e s p ons e , g = 2 2mv 5ns v s = 5v g = +1 v o, dm = 2v p-p r l, dm = 499 ? 5ns/div 0.1%/d iv 0 5 10 15 20 25 30 35 40 01035-050 f i g u re 44. 0. 1% s e t t ling ti me 01035-052 5ns c l = 5pf c l = 0pf c l = 20pf 400mv f i g u re 45. lar g e s i g n al t r ans i ent r e s p ons e for v a ri ous capa citor l o ads (s ee f i gu re 6 0 ) frequency (mhz) p s rr (db) 0.1 1 1 0 100 0 ?1 0 ?2 0 ?3 0 ?4 0 ?50 ?60 ?7 0 ?8 0 ?9 0 1k ? v o, dm ? v s +psrr ? psrr +psrr (v s = 5v, +5v) ? psrr (v s = 5v) 01035-053 fi g u r e 4 6 . p s r r v s . fr e q u e n c y
ad8132 rev. d | page 17 of 32 frequency (mhz) cmrr (db) 1 1 0 100 1000 ?70 ?80 ?50 ?60 ?30 ?40 ? 20 ? v o, dm ? v in, cm ? v o, cm ? v in, cm v s = 5v v in, cm = 2v p-p 01035-055 fi g u r e 4 7 . c m r r v s . fr e q u e n c y ( s e e fi g u r e 6 1 ) frequency (mhz) v ocm gain ( d b) 1 1 0 100 1000 ?9 ?1 2 ?3 ?6 0 ? v o,cm ? v ocm ? v ocm = 600mv p-p ? v ocm = 2v p-p 3 6 ?1 5 v s = 5v 01035-056 f i g u re 48. v ocm g a in resp o n se v s = 5v v ocm = ? 1v to +1v 400mv 5ns v o, cm 01035-057 f i g u re 49. v ocm t r ansi ent respo n se frequency (mhz) v ocm cmrr (db) 1 1 0 100 1000 ?70 ?80 ?50 ?60 ?30 ?40 ?20 ? v ocm = 2v p-p ? v ocm = 600mv p-p ? v o, dm ? v ocm ?10 01035-058 f i g u re 50. v ocm c m rr vs . f r e q ue nc y frequency (hz) in pu t volta ge n o ise ( n v/ h z ) 1k 10 100 10 1 100 1k 10k 100k 1m 10m 8nv/ hz 100m 01035-059 fi g u r e 5 1 . i n p u t v o l t a g e n o i s e v s . fr e q u e n c y frequency (hz) 1k 10 100 10 1 100 1k 10k 100k 1m 10m 100m inp u t curre nt nois e (pa/ hz) 01035-060 1.8pa/ hz f i gure 52. input cu rr e n t no is e v s . f r eq uenc y
ad8132 rev. d | page 18 of 32 5ns v o, dm (0.5v/div) v in, sm (1v/div) v s = 5v v in = 2.5v step g = +2 r f = 1k ? r l, dm = 200 ? 01035-061 f i gure 53. o v e r dr ive r eco ver y temperature ( c) s u p p l y curre nt (ma) 15 13 5 ?50 ? 30 90 ?1 0 1 0 3 0 5 0 7 0 11 9 7 v s = 5v v s = +5v 01035-062 f i gure 54. q u ies c e n t current v s . t e mper atu r e temperature ( c) differential output offset (mv) 0 ?0.5 ?2.5 ? 4 0 ? 20 100 02 0 4 0 6 0 8 0 ?1.0 ?1.5 ?2.0 v s = 5v v s = +5v 01035-063 f i gure 5 5 . di ffer e nt i a l o ffs et v o ltage v s . t e mper ature
ad8132 rev. d | page 19 of 32 test circuits 0.1 f 348 ? 348 ? 49.9 ? 24.9 ? 348 ? 348 ? 499 ? c f c f 01035-005 f i g u re 56. bas i c t e s t circuit , g = 1 0.1 f 499 ? 499 ? 49.9 ? 24.9 ? 1000 ? 1000 ? 200 ? 01035-014 f i g u re 57. bas i c t e s t circuit , g = 2 0.1 f 499 ? 499 ? 49.9 ? 24.9 ? r f 200 ? r f 01035-019 f i gure 58. t e s t c i rc uit for v a ri ous g a in s 0.1 f 49.9 ? 24.9 ? r f r f r g r g r l r l g = +1: r f = r g = 348 ? , r l = 249 ? (r l, dm = 498 ? ) g = +2: r f = 1000 ? , r g = 499 ? , r l = 100 ? (r l, dm = 200 ? ) 01035-021 f i gure 59. t e s t c i rc uit for o u tput ba la nc e 0.1 f 348 ? 348 ? 49.9 ? 24.9 ? 348 ? 348 ? 453 ? 24.9 ? 24.9 ? c l 01035-051 f i gure 60. t e s t c i rc uit for cap a c i to r l o ad d r ive 348 ? 348 ? 49.9 ? 348 ? 348 ? 249 ? 249 ? v o, dm v o, cm note: resistors matched to 0.01%. 01035-054 f i g u re 61. c m r r t e s t cir c u i t 0.1 f 348 ? 348 ? 49.9 ? 24.9 ? 348 ? 348 ? 300 ? 300 ? 2:1 transformer 01035-023 lpf hpf z in = 50 ? f i gur e 6 2 . ha rm onic di stor ti on t e st cir c ui t, g = 1 , r l, dm = 80 0 ? 0.1 f 499 ? 499 ? 49.9 ? 24.9 ? 1000 ? 1000 ? 300 ? 300 ? 2:1 transformer 01035-032 lpf hpf z in = 50 ? f i gur e 6 3 . ha rm onic di stor ti on t e st cir c ui t, g = 2 , r l, dm = 80 0 ?
ad8132 rev. d | page 20 of 32 ope rational descripti o n defi ni tio n of terms d i f f erenti a l v o lt a g e the dif f er ence b e tw e e n tw o n o de v o l t a g es. f o r exa m ple , t h e o u t p ut dif f er en t i al v o l t a g e (o r e q ui valen t l y o u t p u t dif f er en t i al- m o d e vol t a g e) is def i ne d a s v ou t , dm = ( v +o ut ? v ?o ut ) w h er e v +o ut a nd v ?o ut r e fer t o t h e v o l t a g es a t t h e + o u t and ? o u t te r m i n a l s w i t h re sp e c t t o a c o m m on re f e re nc e. co m m o n - m o d e v o l t a g e the a v er a g e o f t w o n o de v o l t a g es. th e ou t p u t c o mm on- m o d e vol t a g e is def i n e d as v ou t , c m = ( v +ou t ? v ?o ut )/2 ad8132 c f +in ?in r f c f r f r g r g +d in v ocm ?d in r l, dm +out v o, dm ?out 01035-064 f i g u re 64. ci r c u i t d e f i nit i ons basic circuit operation on e o f t h e m o re us ef u l a nd e a s y t o un ders t a nd wa ys t o us e t h e ad8132 is t o p r o v ide tw o eq ual - ra tio f e e d bac k n e tw o r ks. t o ma t c h t h e ef fe c t o f p a rasi t i cs, t h es e netw o r ks sho u ld ac t u al l y b e co m p ri sed o f tw o eq ual - v a l u e f eed ba ck r e s i s t o r s , r f , a n d t w o e q ual-val u e ga in r e sis t o r s, r g . this cir c ui t is sh o w n i n f i gur e 64. l i k e a con v en tio n al o p a m p , t h e ad8132 has tw o dif f er en tial in p u ts t h a t can b e dr i v en wi t h b o t h a dif f er en t i al- m o d e in pu t vol t age, v in, d m , and a c o m m on- m o d e i n put vol t age, v in, cm . ther e is an o t h e r in p u t, v oc m , th a t i s n o t p r e s en t o n co n v e n t i o n a l op am p s but pr ov i d e s a n ot he r i n put to c o ns i d e r on t h e a d 8 1 3 2 . i t i s tot a l l y s e p a r a te f r om t h e a b ove i n put s . ther e a r e tw o c o m p le m e n t a r y o u t p uts w h os e res p o n s e can b e def i n e d b y a dif f er en t i a l - m o d e o u t p ut, v ou t , d m , a nd a com m o n - mo d e output , v ou t , c m . t a b l e 9 i n di ca t e s t h e ga i n f r o m a n y ty p e o f in pu t t o ei t h er ty p e of output . ta ble 9. di ffer e nt i a l- a n d co mmo n-m o de g a i n s i n p u t v out, dm v out, c m v in, d m r f /r g 0 (by des i gn) v in, cm 0 0 (by design) v ocm 0 1 (by design) the dif f er en t i al o u t p ut (v ou t , d m ) is e q ual t o t h e dif f er en t i al in p u t v o l t a g e ( v in, d m ) tim e s r f /r g . i n t h i s c a s e , i t d o e s n o t ma t t er if b o t h dif f er en t i al i n p u t s a r e dr i v en, o r o n l y o n e o u t p ut is dr i v en and t h e o t h e r is t i e d t o a r e fer e n c e v o l t a g e , s u ch as g r o u n d . a s is s e en f r o m t h e tw o zer o en t r ies in t h e f i rs t col u mn, n e i t her o f t h e c o mm on- m o d e i n p u ts has an y ef fe c t o n t h is ga i n . the ga i n f r o m v in, d m to v ou t , c m is 0, a n d f i rst - or der do es n o t d e p e nd o n t h e r a t i o m a tch i ng o f t h e fe e d b a ck n e t w or k s . t h e co mm o n -mo d e f eed back lo o p wi t h in t h e ad8 132 p r o v ides a co rr ecti v e a c ti o n t o k e e p th i s ga i n t e rm m i ni mi z e d . th e t e rm b a lan c e er r o r des c r i b e s t h e deg r e e t o w h ich t h is ga in t e r m d i ff e r s fr o m 0 . the ga i n f r o m v in, cm to v ou t , d m dir e c t ly dep e n d s o n t h e m a t c hi n g o f th e f eed ba ck n e tw o r k s . th e a n alogo u s t e rm f o r th i s t r a n sfer f u n c t i on, w h ich is us e d in con v e n t i o n a l o p a m ps, is co m m o n - m o d e r e j e c t io n ra t i o (cmrr). t h er efo r e, if i t has a h i gh c m r r , th e f e e d ba c k r a ti o s m u s t b e w e ll m a t c h e d . the ga i n f r o m v in, cm to v ou t , c m is a l s o ide a l l y 0 a nd is f i rst-o r de r indep e n d en t o f t h e fe e d b a ck ra t i o ma t c hin g . a s in t h e c a s e o f v in, d m to v ou t , c m , t h e co mm on- m o d e fe e d b a ck lo o p k e eps t h is ter m min i mi ze d . the ga i n f r o m v oc m to v ou t , d m i s i d eall y 0 wh en th e f eed ba c k ra t i os a r e ma t c he d o n l y . th e amo u n t o f dif f er en t i al o u t p ut sig n al tha t is cr e a t e d b y va r y in g v oc m is r e la te d to t h e deg r e e o f m i s m a t ch in th e f eed b a c k n e t w o r k s . v oc m co n t r o ls th e o u t p ut co mm on- m o d e v o l t a g e v ou t , c m wi t h a un i t y- ga i n tra n sf e r fun c ti o n . w i th eq ua l- ra ti o f e ed ba ck ne t w or k s ( a s a s s u me d a b ove ) , it s e f f e c t on e a ch output i s t h e s a me , w h ich is an o t h e r w a y o f s a y i ng t h a t t h e g a in f r o m v oc m to v ou t , d m is 0. i f n o t dr i v en, t h e ou t p u t co mm on-m o d e is a t mids u p p l y . i t is r e co mmen d e d tha t a 0.1 f b y p a s s c a p a ci t o r be co nne c t e d to v oc m . w h en u n e q ual fe e d b a ck r a t i os ar e us e d , t h e tw o ga in s ass o c i a t e d w i t h v ou t , d m b e co me n o nz er o . this si g n if ica n t l y co m p li ca t e s t h e m a t h ema t i c al a n al ysi s alo n g w i th a n y i n t u i t i v e un ders t a n d i n g o f h o w t h e p a r t o p era t es.
ad8132 rev. d | page 21 of 32 theory of operation the ad8132 dif f ers f r o m co n v en tio n al o p am ps b y th e ext e r n al p r es en c e o f a n a ddi t i ona l i n p u t a nd o u t p u t . t h e addi t i o n a l in p u t, v oc m , c o n t ro l s t h e output c o m m on - m o d e vo lt age. t h e addi tio n al o u t p u t is the a n alog co m p lem e n t o f th e sin g l e output of a c o n v e n t i on a l op a m p . f o r it s op e r a t i o n , t h e a d 8 1 3 2 us es tw o f eed b a c k lo o p s as co m p a r ed t o the sing le lo o p o f c o n v e n t i on a l op am p s . w h i l e t h i s prov i d e s s i g n i f i c an t f r e e d o m t o cr ea t e va r i o u s n o v e l cir c ui ts, basic o p a m p t h eo r y ca n s t il l be us e d t o a n al y z e t h e o p era t ion. o n e of t h e f e e d b a ck l o op s c o n t ro l s t h e output c o m m on - m o d e vol t age, v ou t , c m . i t s in p u t is v oc m (pin 2) a nd t h e o u t p ut is t h e co mm o n - m o d e , o r a v era g e v o l t a g e , o f t h e tw o dif f er en t i al o u t p u t s (+o u t a nd ?o ut ). th e ga in o f this c i r c ui t is in t e r n al l y s e t t o uni t y . w h en t h e ad8132 is o p er a t in g in i t s li n e a r r e gi o n , thi s e s ta b l i s h e s o n e o f th e o p e r a t io n a l co n s tra i n t s: v ou t , c m = v oc m . the s e cond fe e d b a ck lo o p co n t r o ls t h e dif f er en t i al o p er a t ion. s i mil a r t o a n o p a m p , t h e ga in and ga in-s ha p i ng o f th e tra n sf er f u n c tion can be co n t r o l l ed b y addin g p a s s i v e f e e d back ne t w or k s . h o w e ve r , on ly one f e e d b a c k ne t w or k i s re qu i r e d to clo s e t h e lo o p and f u l l y co n s t r ain t h e o p er a t ion , b u t de p e n d i n g on t h e f u nc t i on d e s i re d, t w o fe e d b a c k ne t w or k s c a n b e u s e d . this is p o ssib le as a r e su l t o f ha vin g tw o o u t p u t s t h a t a r e e a ch in v e r t e d wi t h r e s p e c t t o t h e dif f er en t i a l in p u ts. general usage of the ad8132 s e v e ral as s u m p t i o n s a r e made her e f o r a f i r s t-o r d e r a n al ysis; th ey a r e th e t y p i cal a s s u m p t i o n s used f o r th e a n al ysi s o f o p am p s : ? the i n p u t b i as c u r r en ts a r e s u f f i cien t l y smal l s o t h e y ca n b e ne g l e c te d. ? t h e out p ut i m p e d a nc e s are ar bit r ar i l y low . ? the o p e n -lo o p ga in is a r b i t r a r i l y la rge , w h ich d r i v es t h e a m plif ier t o a st a t e w h er e t h e i n p u t dif f er en t i al v o l t a g e is e f fe c t ively 0 . ? of fs et v o l t a g es a r e as s u m e d t o b e 0. w h ile i t is p o s s ib le t o o p era t e t h e ad8132 wi t h a p u r e l y dif f er en t i a l in put, ma n y o f i t s a pplica t ion s ca l l fo r a cir c ui t t h a t has a sin g le -e n d e d in p u t wi th a dif f er en tial ou t p u t . f o r a sin g le-e n d e d - t o-dif f er en t i al cir c ui t, t h e r g o f t h e undr i v en in p u t is t i e d t o a r e fer e n c e v o l t age . this is g r o u nd an d o t h e r c o n d i ti o n s a r e di scu s sed la t e r . a l so , th e v o l t a g e a t v oc m , a n d t h er efo r e v ou t , cm , is assu m e d to b e g r o u n d fo r no w . f i gur e 65 sh o w s a ge nera lize d s c h e m a t i c o f such a cir c ui t usin g a n ad8132 wi t h tw o f eed back p a t h s. f o r e a ch fe e d b a ck netw o r k, a fe e d b a ck fac t o r can b e def i n e d as th e f r a c ti o n o f t h e o u t p u t si gn al th a t i s f e d b a c k t o th e o p posi t e sig n in p u t. th es e t e r m s a r e: ( ) f1 g1 g1 r r r + = 1 ( ) f2 g2 g2 r r r + = 2 the fe e d b a ck f a c t o r 1 is fo r t h e side t h a t is dr iv en, w h i l e t h e f eed ba ck fa ct o r 2 i s f o r th e s i d e th a t i s tied t o a r e f e r e n c e v o l t a g e (gr o u n d f o r n o w ) . n o t e also th a t ea c h f e ed ba ck fa ct o r ca n v a r y a n y w her e b e tw e e n 0 and 1. a sin g le-e nde d - to -dif fer e n t ia l g a in e q u a t i o n can b e der i ve d , whic h is tr ue f o r al l val u es o f 1 a nd 2. ( ) ( ) 2 1 1 1 2 g + ? = this exp r es sio n is n o t v e r y in t u i t i v e , b u t s o m e f u r t h e r exa m ples ca n p r o v i d e b e t ter un derst a ndi ng o f i t s im pli c a t i o n s . on e obs e r v a t io n t h a t can b e made r i g h t a w a y is t h a t a toler a nce er r o r in 1 do es n o t ha v e t h e s a m e ef fe c t on ga i n as t h e s a me t o lera n c e er r o r in 2. resistorless differe n tial ampl ifier (high inpu t im pe dance inve rting am plifier) the sim p lest clos e d -lo o p cir c u i t t h a t can b e made do es n o t re qu i r e a n y re s i stor s a n d i s s h o w n i n fi g u re 6 8 . i n t h i s c i rc u i t , 1 is eq ual t o 0, a nd 2 is eq u a l t o 1. th e gain is eq ual t o 2. a m o r e in t u i t i v e m e a n s t o f i gur e t h e gain is b y sim p le i n s p ecti o n . +o ut i s co nn ect e d t o ?in , w h ose v o l t a g e i s eq ual t o t h e v o lt a g e a t + i n u n d e r e q u i l i br iu m c o n d it i o n s . t h u s , + v ou t is e q ua l t o v in , and t h er e is u n i t y ga in in t h is p a t h . b e c a us e ? o u t h a s to s w i n g i n t h e opp o s i te d i re c t i o n f rom + o u t d u e t o t h e comm o n -mo d e con s t r a i n t , i t s ef fe c t do ub les t h e o u t p u t sig n al a nd p r o d uces a ga in o f 2. on e us ef u l f u n c t i o n t h a t t h is circ ui t p r o v ides is a hig h in p u t im p e dan c e i n v e r t er . i f +o ut is ig n o r e d , t h er e is a uni t y-ga i n , hig h i n p u t im p e dan c e a m pl if ier fo r m e d f r o m +in t o ?o u t . m o s t t r adi t io na l o p a m p i n v e r ters ha v e r e l a t i vely lo w in p u t i m p e da n c e s , unle s s th ey a r e b u f f e r ed wi th a n o t h e r a m p l i f i e r . v oc m has b e en as s u m e d t o b e a t mids u p ply . b e ca us e t h er e is s t i l l th e co n s tra i n t f r o m th e a b o v e d i scus s i o n th a t +v ou t mu s t e q u a l v in , c h a n g i n g t h e v oc m v o l t a g e do es n o t cha n g e +v ou t (= v in ). ther efo r e , t h e e f fe c t o f cha n g i n g v oc m m u s t s h o w u p a t ?o ut . fo r e x a m p l e , i f v oc m is ra is ed b y 1 v , th en ?v out m u s t g o u p b y 2 v . this ma k e s v ou t , c m als o g o u p b y 1 v , sin c e i t is def i n e d as t h e a v era g e o f t h e tw o dif f er en t i al o u t p u t v o lt ag es. this me a n s t h a t t h e g a i n f rom v oc m t o t h e dif f er en t i al o u t p ut is 2.
ad8132 rev. d | page 22 of 32 other 2 = 1 circuits the p r e c e d in g s i m p le co nf igura t io n wi t h 2 = 1 a nd i t s ga in o f 2 i s th e h i gh es t g a i n ci r c ui t tha t ca n be ma d e un d e r th i s co ndi tio n . s i n c e 1 was eq ual t o 0, o n l y hig h er 1 val u es a r e p o s s i b l e . the cir c ui ts wi t h hig h er val u es o f 1 h a v e ga in s lo w e r th a n 2. h o w e v e r , ci r c ui t s wi th 1 eq ual t o 1 a r e n o t p r a c tical b e ca us e t h e y ha v e n o ef fe c t i v e i n p u t and r e s u l t in a gain o f 0. t o in cr eas e 1 f r o m 0, i t is n e ces s a r y t o add two r e sis t o r s in a f eed ba ck n e tw o r k . a g e n e raliz e d ci r c ui t tha t h a s 1 w i t h a v a l u e hig h er t h a n 0 is s h own i n f i gur e 67. a co u p le o f dif f er en t co n v enien t ga ins tha t c a n be cr e a t e d a r e a gain o f 1, wh en 1 is eq ual t o 1 / 3, a nd a ga in o f 0.5, when 1 eq uals 0.6. w i t h 2 e q u a l to 1 in t h es e cir c ui ts, v oc m s e r v es a s t h e re f e re nc e v o l t a g e f r o m w h ich t o m e as ur e t h e i n p u t v o l t ag e a nd t h e individ u al o u t p u t v o l t a g es. i n gen e ral , w h en v oc m is va r i e d in t h es e cir c u i ts, a dif f er en t i al ou t p u t sig n al g e n e ra t e s in addi t i o n to v ou t , c m cha n gin g t h e s a m e am o u n t as t h e v o l t a g e chan g e o f v oc m . varyi n g 2 w h i l e t h e cir c ui t a b o v e s e t s 2 t o 1, a n o t h e r class o f sim p le cir c ui ts can be made tha t s ets 2 eq ual t o 0. this m e an s tha t th er e is n o f eedbac k f r o m +o ut t o ?in. this clas s o f cir c ui ts is ve r y s i mi l a r to a c o n v e n t i ona l i n ve r t i n g op am p . h o we ve r , t h e ad8132 cir c ui ts ha v e an addi tio n al o u t p u t and co mm on-mo d e in p u t th a t ca n b e a n al yz e d sepa ra t e l y (see f i gur e 69). w i t h ? i n c o n n e c te d to g rou nd , + i n b e c o me s a v i r t u a l g rou n d i n t h e sen s e tha t th e t e r m i s used f o r co n v en ti o n al o p a m ps . b o t h in p u ts m u s t ma i n t a in t h e s a me v o l t a g e fo r e q ui lib r i u m op e r a t i o n ; t h e r e f ore, i f one i s s e t to g rou nd, t h e ot he r i s d r ive n t o g r o u n d . th e i n p u t i m p e dan c e can als o b e s e en t o b e e q ual to r g , j u st as i n a c o n v e n t i o n a l o p a m p . i n th i s ca se , h o w e v e r , th e pos i ti v e i n p u t a n d n e g a ti v e o u t p u t a r e used f o r th e f e e d ba ck n e tw o r k . b e ca us e a co n v en ti o n al o p a m p do es n o t ha ve a n e g a t i ve o u t p u t , o n ly i t s i n v e r t i n g in pu t c a n b e us ed f o r th e f e e d back n e tw o r k. the ad8132 is symm etr i cal , t h er efo r e , t h e fe e d b a ck n e tw o r k o n ei t h er side c a n b e us e d t o p r o d uce t h e s a m e r e s u lts. b e ca us e +in is a summin g j u n c t i o n , b y a n a l og-t o-con v en t i o n a l op am p s , t h e g a i n f rom v in t o ? o ut is ?r f /r g . t h i s h o l d s t r u e re g a rd l e ss of t h e vo lt age o n v oc m , a n d sin c e + o ut m o v e s t h e s a m e a m ou n t i n t h e opp o s i te d i re c t i o n f rom ? o u t , t h e ove r a l l ga in is ?2(r f /r g ). v oc m st i l l gover n s v ou t , c m , s o + o ut m u s t be t h e o n l y o u t p u t th a t m o v e s w h en v oc m is va r i e d . b e ca us e v ou t , c m is t h e a v era g e o f t h e tw o o u t p u t s, +o ut m u st m o v e tw ice as fa r a nd i n t h e s a me dir e c t ion as v oc m to c r e a te t h e prop e r v ou t , c m . th er efo r e , t h e g a i n f rom v oc m t o +o ut m u s t be 2. w i t h 2 eq ual t o 0 i n th e s e ci r c ui t s , th e g a i n ca n th eo r e ti call y be s et t o an y val u e f r o m clos e t o 0 t o inf i ni ty , j u s t as i t can wi t h a co n v en ti o n al o p a m p in th e in v e r t i n g m o d e . h o w e v e r , p r a c ti cal re a l - w or l d l i m i t a t i ons a n d p a r a s i t i c s l i m i t t h e r a nge of accep t ab le ga in t o m o r e m o de s t val u es. 1 = 0 ther e is yet a n ot h e r clas s o f cir c ui ts w h er e t h er e is n o fe e d b a ck f r o m ?o ut t o +in. this is t h e cas e w h er e 1 = 0. th e r e sis t o r les s dif f er en t i al a m plif ier des c r i b e d ab o v e m e ets t h is co ndi t i on, b u t i t was p r es en t e d o n ly wi t h t h e con d i t ion t h a t 2 = 1. recal l tha t this cir c ui t had a ga in eq ual to 2. i f 2 decr eas e s in this cir c ui t f r o m uni t y , a smal l e r p a r t o f +v o u t i s f e d b a c k t o ?in a n d th e g a in in cr ea s e s (see f i g u re 6 6 ) . t h i s c i rc u i t i s ve r y si m i l a r to a non i n v e r t i ng op a m p co nf igura t i o n, excep t fo r t h e p r es ence o f t h e addi t i o n al co m p le m e n t a r y o u t p ut. th er efo r e , t h e o v eral l ga in is t w ice t h a t of a non i n v e r t i ng op am p or 2 ( 1 + r f2 /r g2 ) o r 2 (1/2). o n c e ag ai n , v a r y i n g v oc m do es n o t a f fe c t b o t h o u t p uts in t h e s a m e w a y ; t h e r e f ore, i n a d d i t i on to v a r y i n g v ou t , c m wi t h uni t y ga in, t h er e is als o a n ef fe c t o n v ou t , d m by c h a n g i n g v oc m . estimating the output noise voltage simi l a r t o t h e c a s e o f a con v e n t i o n al o p a m p , t h e dif f er en t i al output e r ror s ( n oi s e a n d of f s e t v o lt age s ) c a n b e e s t i m a te d by m u l t i p ly in g t h e in p u t r e fer r e d t e r m s, a t +in and ?in, b y t h e cir c ui t n o i s e ga i n . th e n o is e gai n is def i n e d as ? ? ? ? ? ? + = g f n r r g 1 t o co m p u te t h e t o t a l o u t p u t r e fe r r e d n o is e fo r t h e cir c ui t o f f i gur e 64, co n s idera t io n m u s t a l s o be g i v e n t o th e co n t r i b u tio n of t h e re s i stor s r f a nd r g . refer to t a bl e 1 0 fo r est i ma te d o u tp ut n o is e v o lt a g e de n s i t ies a t va r i o u s clos e d -lo o p gain s. table 10. reco mme nded resi stor values and noise performance for specific gai n s gain r g (?) r f (?) bandwidth ?3 db (mhz) ou tpu t noise ad81 32 only (nv/ hz ) ou tpu t noise ad81 32 + r g , r f (nv/ hz ) 1 499 499 360 16 17 2 499 1.0 k 160 24.1 26.1 5 499 2.49 k 65 48.4 53.3 10 499 4.99 k 20 88.9 98.6
ad8132 rev. d | page 23 of 32 w h en usin g t h e ad8132 in ga in co nf igura t ions w h er e 1 2 , dif f er en t i al ou t p u t n o i s e a p p e a r s d u e t o i n p u t - r e fer r e d v o l t a g e n o is e in t h e v oc m cir c ui tr y acco r d in g t o t h e f o r m u l a ? ? ? ? ? ? + ? = 2 1 2 1 2 nocm ond v v w h er e v on d is th e o u t p ut dif f er en t i al n o is e , and v no c m is t h e in p u t-r e fer r e d v o l t a g e n o is e on v oc m . calculating an application c i rcuits inpu t impedance the ef fe c t i v e i n p u t i m p e dan c e o f a cir c ui t, s u ch as t h a t i n f i gur e 64, a t +d in an d ?d in , dep e n d s on w h et h e r t h e am plif ier is bein g dr i v en b y a sin g le-en d e d o r dif f er en tial sig n al s o ur ce . f o r b a la n c e d di f f er en t i al i n p u t sig n als, t h e in p u t im p e dan c e (r in, d m ) b etw e e n t h e in p u ts (+ d in an d ? d in ) is sim p l y g dm in, r r = 2 i n t h e c a s e o f a sin g le-en d e d in p u t sig n al (f o r exa m p l e , if ?d in is g r o u n d ed a n d th e i n p u t s i g n a l i s a p p l i e d t o + d in ), t h e in p u t im p e d a n c e b e c o m e s () ? ? ? ? ? ? ? ? ? ? ? ? + ? = f g f g dm in, r r r r r 2 1 the cir c ui t s in pu t im p e dan c e is ef fe c t i v e l y hig h er t h a n i t w o u l d be f o r a con v en t i o n al o p a m p conn ec t e d as an in v e r t er bec a us e a f r a c ti o n o f th e d i f f e r e n ti al o u t p u t v o l t a g e a p p e a r s a t t h e in p u ts as a co m m on- m o d e sig n a l , p a r t ia l l y b o o t st r a pp in g t h e v o l t a g e a c ro ss t h e i n put re s i stor , r g . input common-mode voltage r a nge in single-sup ply a pplic atio ns the ad8132 is o p timize d f o r le v e l-s h if ting g r o u n d r e f e r e n c e d in p u t sig n a l s. f o r a sin g le-e n d e d in p u t t h is w o u l d im ply , fo r exa m ple , t h a t t h e v o l t a g e a t ?d in in f i gur e 64 wo u l d be 0 v w h en t h e am pli f ier s n e g a t i v e p o w e r s u p p ly v o l t a g e (a t v?) was al so se t t o 0 v . setti ng th e outpu t c o mmo n-m o de volta g e the ad8132 s v oc m p i n is in t e r n a l ly b i as e d a t a v o l t a g e a p p r o x ima t e l y e q ual t o t h e mi dsu p ply p o in t (a vera g e val u e o f t h e v o l t a g e on v+ a nd v?). r e lyin g o n t h is in ter nal b i as r e s u l t s in an o u t p u t comm on- m o d e vol t a g e t h a t is wi t h in a p p r o x ima t e l y 100 mv o f the exp e c t e d val u e . i n c a s e s w h e r e more a c c u r a te c o n t ro l of t h e output c o m m on - m o d e le ve l is r e q u ir e d , i t is r e commende d t h a t a n ext e r n a l s o u r c e or re s i stor d i v i d e r ( w it h r so ur c e < 10 k ? ) be used . t h e o u t p ut co mm on- m o d e o f fs et val u es in t h e s p e c if ica t ion s s e c t ion a ssu me t h e v oc m in p u t is dr i v en b y a lo w im p e dan c e volt age s o u r c e . driving a c a pacitive load a p u r e ly ca p a c i t i ve lo ad can r e ac t w i t h t h e pin a nd b o n d -w ir e ind u c t an ce o f t h e ad8132, r e su l t in g in hig h f r eq uen c y r i n g ing in t h e p u ls e r e sp o n s e . o n e wa y t o minimi ze t h i s ef fe c t is t o pl a c e a s m a l l c a p a c i tor a c ro ss e a ch of t h e f e e d b a ck re s i stor s . t h e adde d c a p a ci t a nce sh o u ld b e sm a l l to a v o i d dest a b i l i z ing t h e a m plif ier . an alter na t i v e te chnique is t o place a s m al l r e sis t o r in s e r i e s w i t h t h e a m pl i f i e r s output s , a s s h ow n i n f i g u re 6 0 .
ad8132 rev. d | page 24 of 32 layout, grounding, and bypassing a s a hig h s p e e d p a r t , t h e ad81 32 is s e n s i t i v e to t h e pcb e n v i ron me n t i n w h i c h it o p e r a t e s . r e a l i z i n g it s s u p e r i or sp e c if ic a t ion s r e q u ir es a t t e n t io n t o va r i o u s det a i l s o f go o d hig h sp e e d pcb desi g n . the f i rs t r e q u irem e n t is a g o o d s o lid g r o u nd pl a n e t h a t co v e rs as m u c h o f t h e bo a r d a r ea a r o u nd the ad8132 as p o s s ib le . th e o n ly excep t io n to t h is is t h a t t h e tw o in p u t p i n s (pin s 1 an d 8) shou l d b e ke pt a f e w m i l l i m e t e r s f rom t h e g rou nd p l a n e, a n d g rou nd s h ou l d b e re move d f rom i n ne r l a y e r s an d t h e opp o s i t e side o f t h e b o a r d under t h e in pu t p i n s . t h is mi nimi zes t h e st r a y ca p a c i t a n c e on t h es e n o des and h e l p s p r es er v e t h e ga i n f l a t n e s s v s . th e f r eq uen c y . the p o w e r s u p p l y p i n s sh o u ld b e b y p a s s e d as c l os e as p o s s ib le to t h e d e v i c e to t h e ne ar b y g r ou nd pl ane. g o o d hi g h f r e q u e nc y cera mic c h i p ca p a ci t o rs sh o u ld be us e d . this b y p a s s in g sh o u ld be done wi th a ca p a c i tan c e val u e o f 0.01 f t o 0.1 f f o r eac h su p p ly . f u r t he r a w a y , l o w f r e q ue nc y b y p a ss ing shou l d b e p r o v ided wi th 1 0 f ta n t al u m c a p a ci t o r s f r o m e a c h s u p p l y t o g rou nd. t h e s i g n a l rout i ng s h ou l d b e s h or t and d i re c t i n ord e r to a v oi d p a rasi t i c ef fe c t s. w h ere v er t h er e a r e co m p le m e n t a r y sig n als, a symm etr i cal l a yo u t sh o u ld be p r o v ided t o t h e ext e n t p o s s i b le to maximi ze t h e b a lan c e p e r f o r m a n c e . w h en r u nnin g dif f er en t i al sig n als o v er a lo n g dis t an ce , t h e t r aces o n t h e p c b sh o u ld b e clos e t o g e t h er o r a n y dif f er en t i a l wir i n g s h o u l d b e t w is t e d t o g e th er t o minimize t h e a r e a o f th e lo o p tha t is f o r m ed . this r e d u ces t h e radi a t e d e n erg y a n d mak e s t h e c i r c ui t les s s u s c ep t i b l e t o i n t e r f er en ce . circuits r f1 + r f2 r g1 r g2 01035-065 f i gure 65. t y pic a l f o ur -r esistor f eedb a ck c i rcuit + r f2 r g2 v in 01035-066 f i g u re 66. t y pic a l c i rcuit w i t h 1 = 0 r f1 + r g1 01035-067 f i g u re 67. t y pic a l c i rcuit w i t h 2 = 1 + v in 01035-068 f i gur e 6 8 . resi st or less g = 2 c i r c ui t wi t h 1 = 0 r f1 + r g1 v in 01035-069 f i g u re 69. t y pic a l c i rcuit w i t h 2 = 0
ad8132 rev. d | page 25 of 32 appli c ations a/d dri v er m a n y o f t h e ne w e r hig h sp e e d ad cs a r e si n g le-su p ply and ha ve dif f er en t i al in puts. th us, t h e dr iv er fo r t h es e de vices sh o u ld b e a b le to con v er t f r o m a sin g le -e nde d to a dif f er en t i a l sig n a l and prov i d e output c o m m on - m o d e l e vel - sh i f t i ng i n a d d i t i o n to ha vin g lo w disto r tio n a nd n o is e . the ad8132 co n v enien t l y p e r f o r m s th es e f u n c tio n s w h en dr i v in g the ad9203, a 10-b i t, 40 ms ps ad c. i n f i gur e 71, a 1 v p-p sig n al dr i v es th e in p u t o f a n ad8132 co nf igur ed f o r uni t y ga in. b o th th e ad8132 and the ad9203 a r e p o w e r e d f r o m a sin g l e 3 v su p p ly . a vol t a g e di v i der b i a s es v oc m a t mids u p p l y , whic h in t u r n dr i v es v ou t , c m t o half o f th e s u p p ly v o l t a g e . this is wi t h in t h e comm o n - m o d e ra n g e o f t h e ad9203. b etw e e n t h e a/ d an d t h e dr i v er is a 1-p o le , dif f er en t i a l f i l t er t h a t h e l p s t o f i l ter s o m e o f t h e no is e an d as sis t s t h e s w i t ch e d - ca p a c i t o r in p u ts o f t h e a / d . e a ch o f t h e a/ d in p u ts is dr i v e n b y a 0.5 v p-p sig n al tha t ra n g es f r o m 1.25 v dc t o 1.75 v dc. f i g u re 7 0 i s an f f t pl ot of t h e p e r f or m a nc e of t h e c i rc u i t w h e n r u nnin g a t a clo c k ra te o f 40 ms ps an d an i n pu t f r e q uen c y o f 2.5 mh z. 10 0 0 ?1 0 ?2 0 ?3 0 ?4 0 ?5 0 ?6 0 ?7 0 ?8 0 ?9 0 ? 100 ? 110 ? 120 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 fund 2nd 3rd 4th 5th 7th 8th 9th 6th f s = 40mhz f in = 2.5mhz input frequency (mhz) outp ut (dbc ) 01035-071 f i gur e 7 0 . ft t re spo n se f o r ad8 132 d r i v i n g ad92 03 balanced cable driver w h en dr i v i n g a twi s te d p a ir cab l e, i t is desir a b l e to dr i v e o n ly a p u r e dif f er en t i al sig n al o n t o t h e lin e . i f t h e sig n a l is p u r e ly dif f er en t i al ( i .e ., f u l l y b a la n c e d ), a nd t h e t r a n smis sio n li n e is t w iste d and b a l a n c e d , t h er e is a mini m u m r a di a t io n o f an y sig n al . the c o m p l e me n t ar y el e c t r i c a l f i el ds are mo st l y c o nf i n e d to t h e s p ace b etwe e n t h e tw o t w ist e d c o nd uc t o rs an d do es n o t sig n if ica n t l y radia t e o u t f r o m t h e ca b l e . the c u r r en t i n t h e cab l e cr ea t e s m a g n etic f i e l d s th a t ra dia t e t o so m e d e g r ee . h o w e v e r , th e a m o u n t o f ra d i a t i o n i s mi tig a t e d b y th e tw is t s , be ca use f o r ea c h tw is t , t h e tw o a d j a cen t tw is t s h a v e a n o p p o s i t e po la ri t y ma g n et ic f i e l d . i f t h e t w ist p i t c h is t i g h t e n o u g h , t h es e smal l ma g n et ic f i e l d l o o p s co n t a i n mos t o f t h e ma g n et ic f l ux, a n d t h e ma g n et ic fa r - f i eld st r e n g t h is ne g l ig i b le . 3v 0.1 f 10 f + 3v 348 ? 0.1 f 348 ? 49.9 ? 348 ? 24.9 ? 10k ? 10k ? 1v p-p 348 ? 60.4 ? 60.4 ? 20pf 20pf ainn ainp avdd drvdd avss drvss ad9203 digital outputs 3v 0.1 f 0.1 f ad8132 8 2 1 3 5 6 4 25 26 28 27 1 2 01035-070 f i g u re 71. a d 8 1 3 2 d r iv ing a d 9 2 0 3 , a 10-b i t , 40 m s ps a d c
ad8132 rev. d | page 26 of 32 499 ? 523 ? 1k ? 1k ? 10 f + +5v ad8132 0.1 f 49.9 ? 50 ? s ource 0.1 f + 0.1 f 10 f ?5v 49.9 ? 49.9 ? twisted pair 100 ? 1 2 3 4 7 5 ad830 + 0.1 f 10 f ?5v 10 f + +5v 0.1 f v out 01035-072 f i g u re 72. ba la nc e d line d r iver and r e c e iver u s ing a d 8 1 32 and a d 8 30 an y i m b a lan c e in t h e dif f er en t i al dr i v e sig n al a p p e a r s as a co mm o n -mo d e sig n al o n t h e cab l e . this is t h e e q ui valen t o f a sin g le w i r e t h a t is dr i v en wi t h t h e comm o n - m o d e sig n al. i n t h is cas e , t h e wir e ac ts as an a n t e nna a nd radia t es. th us, in o r d er t o mini mi ze r a d i a t io n w h e n dr iving dif f er en t i a l t w iste d p a ir ca b l es, t h e dif f er en t i al dr i v e sig n al s h o u l d b e v e r y w e l l - bala n c e d . the co mm on-m o d e f e e d back lo o p in the ad8 132 h e l p s t o mini mi ze t h e am o u n t o f co mm on- m o d e v o l t a g e a t t h e o u t p ut, a nd can t h er efo r e b e us e d t o cr e a t e a w e l l - b a l a n c e d dif f er en t i a l lin e dr i v er . f i gur e 72 s h o w s an a p p l ic a t ion tha t us es a n ad8132 as a ba lan c e d lin e dr i v er a nd an ad830 as a dif f er en tial r e cei v er co nf igur ed fo r uni t y ga in. this cir c ui t was op era t e d wi t h 10 m of c a te gor y 5 c a bl e. transmi t e q ualizer an y len g t h o f t r a n smis sio n l i n e a t t e n u a t es t h e sig n als i t ca r r ies. this ef fe c t is w ors e a t hig h er f r e q uen c ies t h an a t lo w f r e q uen c ies. o n e wa y t o com p e n s a te fo r t h is is t o p r o v ide an eq ualiz e r ci r c ui t th a t boos t s t h e h i gh e r f r eq ue n c i e s i n t h e t r a n smi t t e r cir c ui t, s o t h a t a t t h e r e cei v e e nd o f t h e ca b l e , t h e a tten u a t io n ef fe c t s a r e dim i nishe d . b y lo w e ri n g th e i m pe da n c e o f th e r g co m p o n en t o f th e f eed ba ck n e tw o r k a t a h i g h e r f r eq ue n c y , t h e g a in ca n be in cr eas e d a t a hig h f r eq uen c y . f i gur e 73 s h o w s t h e ga in o f a tw o lin e dr i v er t h a t has i t s r g r e sis t o r s s h un ted b y 10 pf ca p a ci t o rs. t h e e f f e c t of t h i s i s sho w n i n t h e f r e q u e nc y re sp ons e pl ot of f i gur e 74. 249 ? 49.9 ? 10pf 499 ? 10pf 249 ? 24.9 ? v in 49.9 ? 499 ? 49.9 ? 100 ? v out 01035-073 fi g u r e 7 3 . fr e q u e n c y b o o s t c i r c u i t 1 1000 20 10 0 ?1 0 ?2 0 ?3 0 ?4 0 ?5 0 ?6 0 ?7 0 ?80 v out /v in (db) 10 100 frequency (mhz) 01035-074 f i gur e 7 4 . f r equenc y resp o n se for tr ansm i t boo s t ci r c ui t low-pass diff erential f i lter si m i l a r to an op am p , v a r i ou s t y p e s of a c t i ve f i lt e r s c a n b e cr ea t e d wi th t h e ad8132. th es e ca n ha v e sin g le-ende d in p u ts a nd dif f er en t i a l o u t p uts, w h ich ca n p r o v i d e an a n t i a l i a s f u n c t i on w h en dr i v i n g a dif f er en t i al ad c. f i g u r e 75 i s a sch e ma ti c o f a lo w - pa s s , m u l t i p le f eed b a c k f i l t e r . the ac t i ve s e c t i o n co n t a i n s tw o p o les, a n d a n a ddi t i ona l p o le is adde d a t t h e o u tp u t . t h e f i l ter w a s desig n e d to ha ve a ?3 db f r eq uen c y o f 1 mh z. the ac t u a l ?3 db f r eq uenc y was m e as ur e d t o be 1.12 m h z, as sh o w n in f i gur e 76. 33pf 2.15k ? 953 ? 953 ? 33pf 2.15k ? 100pf 100pf 2k ? 2k ? 24.9 ? 49.9 ? 549 ? 549 ? 200pf 200pf v in v out 01035-075 f i g u re 75. 1 m h z, 3 - p o l e d i f f e r e nt ia l o u t p ut , l o w-p a s s , m u lt ip le f eedb a ck f ilt er
ad8132 rev. d | page 27 of 32 frequency (hz) 10 10k 0 ?1 0 ?2 0 ?3 0 ?4 0 ?5 0 ?6 0 ?7 0 ?8 0 ?9 0 100k 1m 10m 100m v out /v in (db) 01035-076 f i gur e 7 6 . f r equenc y resp o n se o f 1 m h z l o w - p a ss f i l t er high co mm on-m ode o u tput impe dance amplifier ch a n gi n g t h e co n n ect i o n t o v oc m (p in 2) ca n cha n g e t h e co m m o n - m o d e f r o m lo w im p e dan c e to hig h i m p e dance. i f v oc m is ac ti v e l y s et t o a p a r t ic u l a r v o l t a g e , t h e ad8132 tr ies t o f orc e v out , c m t o th e sa m e v o l t a g e wi th a r e la ti v e l y lo w o u t p u t im p e d a n c e . a l l t h e p r e v io us a n a l ysis assume d t h a t t h is o u t p ut im p e dan c e is a r b i t ra r i ly lo w eno u g h t o dr i v e t h e lo ad co ndi t i on in t h e cir c ui t. h o w e v e r , t h er e a r e s o me a pplic a t io n s t h a t b e n e f i t f r o m a hig h co mm o n -mo d e o u t p u t im p e dan c e . this c a n be acco m p lish e d w i th th e c i r c u i t s h o w n i n f i g u r e 7 7 . r g 348 ? r f 348 ? r f 348 ? r g 348 ? 10 ? 10 ? 1k ? 1k ? 49.9 ? 49.9 ? 01035-077 f i gure 77. h i gh co mm on-m od e , o u t p ut imped a nce , d i f f er ent i a l a m p lif ier v oc m is dr i v en b y a r e sisto r di vi der t h a t m e a s ur es t h e o u t p ut c o m m on - m o d e vo lt age. t h u s , t h e c o m m on - m o d e output v o l t a g e t a k e s on t h e val u e t h a t i s s et b y t h e dr i v en cir c ui t. i n t h i s cas e , i t com e s f r o m t h e ce n t er p o in t o f t h e t e r m ina t ion a t t h e re c e ive e n d of a 1 0 m l e ng t h of c a te gor y 5 t w i s te d p a i r c a bl e. i f t h e r e cei v e e n d , co mm o n - m o d e v o l t a g e is s et t o g r o u n d , i t is w e l l -def i n e d a t t h e r e ce i v e e n d . an y co mm on- m o d e sig n al t h a t is p i ck e d u p o v e r t h e cab l e len g t h d u e t o n o is e a p p e a r s a t t h e tra n s m i t en d a n d m u s t be a b so rbe d b y th e tra n sm i t t e r . t h us , i t i s i m po r t a n t tha t th e tra n s m i t t e r h a v e a d e q ua t e co mm o n -m od e o u t p ut ra n g e t o a b s o rb t h e f u l l am pli t ude o f t h e co mm o n - m o d e sig n al co u p le d o n t o t h e cab l e and t h er efo r e p r e v en t cli p p i ng. an o t h e r wa y t o lo o k a t this is tha t t h e cir c ui t p e r f o r m s wha t is s o me t i me s c a l l e d t r ans f or me r a c t i on . o n e m a i n d i f f e r e n c e i s t h a t t h e ad813 2 p a s s es dc w h i l e t r a n sfo r m e rs do n o t. a tra n s f o r m e r ca n also b e ea s i l y co n f i g ur ed t o ha v e ei th e r a hig h o r lo w co mm o n -mo d e o u t p u t im p e dan c e . i f th e tra n sf o r m e r s cen t er t a p is co nnec t e d t o a s o lid v o l t a g e r e fer e n c e , i t s ets t h e co mmo n - m o d e v o l t a g e on t h e s e conda r y s i d e o f th e tra n sf o r m e r . i n th i s ca se , i f o n e o f th e d i f f e r e n ti al o u t p u t s is g r o u n d e d , t h e o t h e r o u t p u t wil l ha ve o n l y half o f th e dif f er en t i al ou t p u t sig n al. this k e eps t h e commo n - m o d e v o l t a g e a t g r o u nd , w h ere i t is r e q u ir e d to b e d u e t o t h e cen t er t a p co nnec t io n. this is a n alog o u s t o th e ad8132 op era t in g wi t h a lo w o u t p u t i m p e dan c e co mm on- m o d e (s e e f i g u r e 78). v diff v ocm 01035-078 f i gure 78. t r ans f o r me r w h os e l o w o u tput imped a nce s econd ar y is s e t at v oc m i f t h e ce n t er t a p o f t h e s e conda r y o f a t r a n sfo r m e r is al lo w e d t o f l o a t as s h own i n f i gur e 79 (o r if t h er e is n o ce n t er t a p), t h e t r a n sfo r m e r wi l l ha ve a hig h comm on- m o d e ou t p ut im p e dan c e. t h i s m e a n s th a t th e co mm o n m o d e o f th e seco n d a r y i s deter m i n e d b y w h a t i t is con n e c te d to and n o t b y a n y t hing to do w i th th e t r a n s f o r m e r i t se l f . i f o n e o f th e d i f f e r e n ti al en d s o f th e tra n s f o r m e r i s gr o u n d ed , th e o t h e r en d sw in g s wi th t h e f u ll o u t p u t v o l t a g e . t h i s m e a n s t h a t t h e co mm on- m o d e o f t h e ou t p ut v o l t a g e is o n e - half o f t h e d i f f e r e n ti al o u t p u t v o l t a g e . h o w e v e r , th i s s h o w s th a t t h e co m m o n - m o d e is n o t fo r c e d v i a a lo w im p e dan c e to a g i v e n v o l t a g e . th e comm on- m o d e ou t p ut v o l t a g e can b e cha n ge d e a s i ly to an y vo lt age t h rou g h it s ot he r output t e r m i n a l s . the ad8132 can exhib i t the s a m e p e r f o r ma n c e w h en one o f th e output s i n fi g u re 7 7 i s g rou nd e d . t h e ot he r output s w i n g s a t t h e f u l l dif f er en t i al o u t p ut v o l t a g e . the co mm on- m o d e sig n al is m e as ur e d b y t h e v o l t a g e divide r acr o s s t h e o u t p u t s and in p u t to v oc m . this t h en dr i v es v ou t , c m t o th e s a m e l e v e l. a t hig h er f r e q uen c ies, i t is im p o r t an t t o minimize t h e c a p a ci t a n c e o n t h e v oc m n o de o r e l s e phas e s h if ts c a n com p r o m is e t h e p e r f o r ma n c e . th e v o l t a g e divider r e sis t a n ces can als o b e l o we re d f o r b e tt e r f r e q u e nc y re sp ons e . v diff nc 01035-079 f i gure 79. t r ansfo r me r w i th h i gh o u t p ut imped a nce s econdar y f u ll-wave rectif ier the bal a n c e d ou t p u t s o f th e ad8132, alo n g wi th a co u p le o f s c h o t t k y dio d es , ca n cr ea t e a v e r y hig h s p ee d , f u l l -wa v e r e c t if ier . s u ch cir c ui ts a r e us ef u l fo r m e as ur in g ac v o l t a g es a nd o t h e r co m p u t a t io nal t a s k s.
ad8132 rev. d | page 28 of 32 f i g u re 8 0 show s t h e c o n f i g u r a t i o n of su ch a c i r c u i t . e a ch of t h e ad8132 o u t p u t s dr i v es th e a n o d e o f a n hp283 5 s c h o t t k y dio d e . th e s e s c h o t t k y dio d es w e r e ch o s en fo r t h eir hig h s p e e d o p era t ion. a t lo w e r f r e q uen c ies (a p p r o x ima t e l y lo w e r t h a n 10 mh z), a si lic o n sig n a l dio d e, such as a 1 n 41 48, ca n b e us e d . the c a t h o d es o f t h e tw o dio d e s a r e co nn e c t e d tog e t h er , a nd t h i s o u t p u t no de is c o nn ec t e d t o g r o u n d b y a 100 ? r e sis t o r . r g1 348 ? r f1 348 ? r f2 348 ? r g2 348 ? +5v ?5 v r l 100 ? r t2 24.9 ? r t1 49.9 ? v in hp2835 v out +5v cr1 10k ? 01035-080 f i g u re 80. f u ll-w a ve r e c t if i e r t h e d i o d e s s h o u ld be o p e r a t ed s u c h th a t th ey a r e s l i g h t l y fo r w a r d-b i as e d w h en t h e dif f er en t i al o u t p u t v o l t a g e is 0. f o r t h e s c h o t t k y dio d es , this is a p p r o x ima t e l y 400 mv . the f o r w a r d b i asin g ca n b e c o n v en ien t ly a d j u st e d b y cr1, w h ich, in t h is cir c ui t, ra is es and lo w e rs v out , c m wi t h o u t cr e a t i ng a dif f er en t i al output vo lt ag e. on e ad van t a g e o f t h is cir c ui t is t h a t t h e fe e d b a ck lo o p is ne v e r m o m e n t a r i l y o p en e d w h i l e t h e dio d es r e vers e t h eir p o la r i ty wi t h in t h e lo o p . this is t h e s c h e m e t h a t is s o me t i m e s us e d fo r f u l l -wa v e r e c t if i e rs t h a t us e con v en t i o n al o p am ps. th es e co n v en ti o n al ci r c ui t s d o n o t w o r k w e ll a t f r eq uen c i e s a b o v e a pprox i m a t el y 1 m h z . i f t h er e is n o t e n o u g h fo r w a r d- b i as (v ou t , c m t o o lo w), th e lo w e r s h a r p c u s p s o f th e f u l l - w a v e r e c t if ie d o u t p u t wa v e fo r m wi l l b e r o u n d e d o f f . also , a s th e f r eq uen c y in cr ea se s , t h e r e t e n d s t o b e s o m e rou nd i n g of t h e l o we r c u sp s . t h e f o r w ard bi a s c a n b e i n c r e a s e d to y i el d shar p e r c u sp s a t hi g h e r f r e q u e nc i e s . ther e is n o t a r e lia b le , e n t i r e ly qua n t i f i a b l e me an s t o me as ur e t h e p e r f o r ma n c e o f a f u l l -wa v e r e c t if ier . sin c e t h e i d e a l w a v e f o rm h a s pe ri od i c s h a r p d i sc o n tin u i t i e s , i t s h o u l d h a v e (m os tl y ev en ) h a rm o n i c s tha t ha v e n o u p pe r bo un d o n t h e f r e q uen c y . h o w e v e r , fo r a p r ac t i ca l cir c ui t, as t h e f r e q uen c y i n cr ease s , th e h i gh e r h a rm o n i c s beco m e a t t e n u a t e d a n d th e s h a r p c u s p s t h a t a r e p r es en t a t l o w f r e q uen c ies b e come sig n if ica n t l y r o un de d . the cir c ui t was r u n a t a f r eq uenc y u p t o 300 mh z and , while i t w a s s t ill fun c ti o n al , th e ma jo r ha rm o n i c tha t r e m a in ed i n t h e o u t p u t was t h e s e co nd . this made i t lo o k l i k e a sin e wa ve a t 600 mh z. f i gure 81 is a n os cil l os co p e p l o t o f th e o u t p u t w h en dr i v en b y a 100 mh z, 2.5 v p-p in p u t. so m e tim e s a sec o n d h a rm o n i c g e n e ra t o r i s a c t u all y u s e f ul f o r cr e a t i n g a clo c k t o o v ers a m p le a d a c b y a fac t or o f tw o . i f t h e output of t h i s c i rc u i t i s r u n t h rou g h a l o w - p a ss f i lte r , it c a n b e us e d as a s e cond ha r m onic ge ner a to r . 100mv 2ns 1v 01035-081 f i gure 81. f u ll-w a ve rec t ifi e r respons e with 1 0 0 mh z inp u t
ad8132 rev. d | page 29 of 32 outline dimensions 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 0.50 (0.0196) 0.25 (0.0099) 45 8 0 1.75 (0.0688) 1.35 (0.0532) seating plane 0.25 (0.0098) 0.10 (0.0040) 4 1 85 5. 00 ( 0 . 1 9 68) 4. 80 ( 0 . 1 8 90) 4.00 (0.1574) 3.80 (0.1497) 1.27 (0.0500) bsc 6.20 (0.2440) 5.80 (0.2284) 0.51 (0.0201) 0.31 (0.0122) coplanarity 0.10 controlling dimensions are in millimeters; inch dimensions (in parentheses) are rounded-off millimeter equivalents for reference only and are not appropriate for use in design compliant to jedec standards ms-012aa f i g u re 82. 8-l e ad s t anda r d s m a l l o u t l ine p a ckag e [soic ] narro w b o dy (r -8) di me nsio ns sho w n i n mi ll im e t e r s a n d (i nc he s) 0.80 0.60 0.40 8 0 4 8 1 5 4.90 bsc pin 1 0.65 bsc 3.00 bsc seating plane 0.15 0.00 0.38 0.22 1.10 max 3.00 bsc coplanarity 0.10 0.23 0.08 compliant to jedec standards mo-187aa f i g u re 83. 8-l e ad m i ni s m al l o u t l ine p a ckag e [m so p ] (rm-8) di me nsio ns sho w n i n mi ll im e t e r s ordering guide model temperature r a nge package desc ri p t i o n p a c k a g e o p t i o n b r a n d i n g ad8132ar ?40c to +125c 8-lead soic r-8 ad8132ar-reel ?40c to +125c 8-lead so ic, 13 " tape and reel of 2,500 r-8 ad8132ar-reel 7 ?40c to +125c 8-lead so ic, 7" tape and reel of 1,000 r-8 ad8132arz 1 ?40c to +125c 8-lead soic r-8 ad8132arz-re e l 1 ?40c to +125c 8-lead soic, 13 " tape and reel of 2,500 r-8 ad8132arz-re el7 1 ?40c to +125c 8-lead soic, 7" tape and reel of 1,000 r-8 ad8132arm ?40c to +125c 8-lead msop rm-8 hma ad8132arm- r e el ?40c to +125c 8-lead msop , 1 3 " tape and ree l of 3,000 rm-8 hma ad8132arm- r e el7 ?40c to +125c 8-lead msop , 7 " tape and reel of 1,000 rm-8 hma ad8132armz 1 ?40c to +125c 8-lead msop rm-8 hma ad8132armz-reel 1 ?40c to +125c 8-lead msop, 1 3 " tape and ree l of 3,000 rm-8 hma ad8132armz-r eel7 1 ?40c to +125c 8-lead msop, 7 " tape and reel of 1,000 rm-8 hma 1 z = pb-free part
ad8132 rev. d | page 30 of 32 notes
ad8132 rev. d | page 31 of 32 notes
ad8132 rev. d | page 32 of 32 notes ? 2004 analo g de vices, inc. all rights reserve d . tra d em arks and registered tra d ema r ks are the prop erty of their respective owners . c01035C0 C 12/04(d)

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