1 LT1225 very high speed operational amplifier n gain of 5 stable n 150mhz gain bandwidth n 400v/ m s slew rate n 20v/mv dc gain, r l = 500 w n 1mv maximum input offset voltage n 12v minimum output swing into 500 w n wide supply range: 2.5v to 15v n 7ma supply current n 90ns settling time to 0.1%, 10v step n drives all capacitive loads d u escriptio s f ea t u re the LT1225 is a very high speed operational amplifier with excellent dc performance. the LT1225 features reduced input offset voltage and higher dc gain than devices with comparable bandwidth and slew rate. the circuit is a single gain stage with outstanding settling characteristics. the fast settling time makes the circuit an ideal choice for data acquisition systems. the output is capable of driving a 500 w load to 12v with 15v supplies and a 150 w load to 3v on 5v supplies. the circuit is also capable of driving large capacitive loads which makes it useful in buffer or cable driver applications. the LT1225 is a member of a family of fast, high per- formance amplifiers that employ linear technology corporations advanced bipolar complementary processing. u s a o pp l ic at i n wideband amplifiers n buffers n active filters n video and rf amplification n cable drivers n data acquisition systems u a o pp l ic at i ty p i ca l 20mhz,a v = 50 instrumentation amplifier gain of 5 pulse response + + + LT1225 LT1225 LT1225 1k v in 1k v out 200pf 250 w 250 w 1k 1k 10k 10k + LT1225 ta01 LT1225 ta02
LT1225 2 total supply voltage (v + to v C ) .............................. 36v differential input voltage ......................................... 6v input voltage ............................................................ v s output short circuit duration (note 1) ............ indefinite operating temperature range LT1225c ................................................ 0 c to 70 c maximum junction temperature plastic package .............................................. 150 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec.)................. 300 c a u g w a w u w a r b s o lu t exi t i s wu u package / o rder i for atio order part number symbol parameter conditions min typ max units v os input offset voltage (note 2) 0.5 1.0 mv i os input offset current 100 400 na i b input bias current 48 m a e n input noise voltage f = 10khz 7.5 nv/ ? hz i n input noise current f = 10khz 1.5 pa/ ? hz r in input resistance v cm = 12v 24 40 m w differential 70 k w c in input capacitance 2pf input voltage range + 12 14 v input voltage range C C13 C12 v cmrr common-mode rejection ratio v cm = 12v 94 115 db psrr power supply rejection ratio v s = 5v to 15v 86 95 db a vol large signal voltage gain v out = 10v, r l = 500 w 12.5 20 v/mv v out output swing r l = 500 w 12.0 13.3 v i out output current v out = 12v 24 40 ma sr slew rate (note 3) 250 400 v/ m s full power bandwidth 10v peak, (note 4) 6.4 mhz gbw gain bandwidth f = 1mhz 150 mhz t r , t f rise time, fall time a vcl = 5, 10% to 90%, 0.1v 7 ns overshoot a vcl = 5, 0.1v 20 % propagation delay 50% v in to 50% v out 7ns t s settling time 10v step, 0.1%, a v = C 5 90 ns differential gain f = 3.58mhz, a v = 5, r l = 150 w 1.0 % differential phase f = 3.58mhz, a v = 5, r l = 150 w 1.7 deg r o output resistance a vcl = 5, f = 1mhz 4.5 w i s supply current 79 ma e lectr ic al c c hara terist ics v s = 15v, t a = 25 c, v cm = 0v unless otherwise noted. s8 part marking 1225 LT1225cn8 LT1225cs8 1 2 3 4 5 6 7 8 top view null v + null ?n out nc +in v s8 package
8-lead plastic soic n8 package
8-lead plastic dip LT1225 po01 t j max = 15o c, q ja = 130 c/ w (n8) t j max = 15o c, q ja = 220 c/ w (s8)
3 LT1225 symbol parameter conditions min typ max units v os input offset voltage v s = 15v, (note 2) 0.5 1.5 mv v s = 5v, (note 2) 1.0 2.5 mv input v os drift 10 m v/ c i os input offset current v s = 15v and v s = 5v 100 600 na i b input bias current v s = 15v and v s = 5v 4 9 m a cmrr common-mode rejection ratio v s = 15v, v cm = 12v and v s = 5v, v cm = 2.5v 93 115 db psrr power supply rejection ratio v s = 5v to 15v 85 95 db a vol large signal voltage gain v s = 15v, v out = 10v, r l = 500 w 10 12.5 v/mv v s = 5v, v out = 2.5v, r l = 500 w 8 10 v/mv v out output swing v s = 15v, r l = 500 w 12.0 13.3 v v s = 5v, r l = 500 w or 150 w 3.0 3.3 v i out output current v s = 15v, v out = 12v 24 40 ma v s = 5v, v out = 3v 20 40 ma sr slew rate v s = 15v, (note 3) 250 400 v/ m s i s supply current v s = 15v and v s = 5v 7 10.5 ma v s = 5v, t a = 25 c, v cm = 0v unless otherwise noted. symbol parameter conditions min typ max units v os input offset voltage (note 2) 1.0 2.0 mv i os input offset current 100 400 na i b input bias current 48 m a input voltage range + 2.5 4 v input voltage range C C 3 C 2.5 v cmrr common-mode rejection ratio v cm = 2.5v 94 115 db a vol large-signal voltage gain v out = 2.5v, r l = 500 w 10 15 v/mv v out = 2.5v, r l = 150 w 13 v/mv v out output voltage r l = 500 w 3.0 3.7 v r l = 150 w 3.0 3.3 v i out output current v out = 3v 20 40 ma sr slew rate (note 3) 250 v/ m s full power bandwidth 3v peak, (note 4) 13.3 mhz gbw gain bandwidth f = 1mhz 100 mhz t r , t f rise time, fall time a vcl = 5, 10% to 90%, 0.1v 9 ns overshoot a vcl = 5, 0.1v 10 % propagation delay 50% v in to 50% v out 9ns t s settling time C 2.5v to 2.5v, 0.1%, a v = C 4 70 ns i s supply current 79 ma e lectr ic al c c hara terist ics e lectr ic al c c hara terist ics note 3: slew rate is measured between 10v on an output swing of 12v on 15v supplies, and 2v on an output swing of 3.5v on 5v supplies. note 4: full power bandwidth is calculated from the slew rate measurement: fpbw = sr/2 p vp. note 1: a heat sink may be required to keep the junction temperature below absolute maximum when the output is shorted indefinitely. note 2: input offset voltage is tested with automated test equipment in <1 second. 0 c t a 70 c, v cm = 0v unless otherwise noted.
LT1225 4 cc hara terist ics uw a t y p i ca lper f o r c e output short-circuit current vs supply current vs temperature input bias current vs temperature temperature output voltage swing vs input bias current vs input open-loop gain vs resistive load common-mode voltage resistive load input common-mode range vs output voltage swing vs supply voltage supply current vs supply voltage supply voltage supply voltage (?) 0 0 magnitude of input voltage (v) 5 10 15 20 5101520 LT1225 tpc01 t a = 25?
d v os < 1mv +v cm ? cm supply voltage (?) 0 6.0 supply current (ma) 6.5 7.0 7.5 8.0 5101520 LT1225 tpc02 t a = 25? supply voltage (?) 0 0 output voltage swing (v) 5 10 15 20 5101520 LT1225 tpc03 t a = 25?
r l = 500 w
d v os = 30mv +v sw ? sw load resistance ( w ) 10 0 output voltage swing (vp-p) 10 20 25 30 100 1k 10k LT1225 tpc04 15 5 t a = 25?
d v os = 30mv v s = ?5v v s = ?v input common-mode voltage (v) ?5 3.0 input bias current ( m a) 3.5 4.0 4.5 5.0 ?0 0 10 15 LT1225 tpc05 ? 5 v s = ?5v
t a = 25?
i b+ + i b? 2 i b = load resistance ( w ) 10 50 open-loop gain (db) 80 90 100 100 1k 10k LT1225 tpc06
70 60 t a = 25? v s = ?5v v s = ?v temperature (?) ?0 25 output short-circuit current (ma) 35 40 50 55 ?5 25 75 125 LT1225 tpc09 100 50 0 30 45 v s = ?v sink source temperature (?) ?0 3.5 input bias current ( m a) 4.0 4.25 4.75 5.0 ?5 25 75 125 LT1225 tpc08 100 50 0 3.75 4.5 v s = ?5v
i b+ + i b? 2 i b = temperature (?) ?0 4 supply current (ma) 6 7 9 10 ?5 25 75 125 LT1225 tpc07 v s = ?5v 100 50 0 5 8
5 LT1225 cc hara terist ics uw a t y p i ca lper f o r c e closed-loop output impedance vs frequency gain bandwidth vs temperature slew rate vs temperature power supply rejection ratio vs common-mode rejection ratio vs input noise spectral density frequency frequency temperature (?c) ?0 gain bandwidth (mhz) 151 152 153 25 75 LT1225 tpc17 150 149 ?5 0 50 100 125 148 147 v s = ?5v temperature (?c) ?0 slew rate (v/ m s) 400 450 500 25 75 LT1225 tpc18 350 300 ?5 0 50 100 125 250 200 ?r +sr v s = ?5v
a v = ? frequency (hz) input voltage noise (nv/ ? hz) 1 100 10 1k 10k 100k LT1225 tpc10 100 1000 10 v s = ?5v
t a = 25?
a v = 101
r s = 100k i n e n 0.01 1.0 10 0.1 input current noise (pa/ ? hz) frequency (hz) 1k 0 common mode rejection ratio (db) 20 40 60 80 100 120 10k 100k 1m 10m ltxxxx ?tpcxx 100m v s = ?5v
t a = 25? frequency (hz) 100 0 power supply rejection ratio (db) 20 40 60 80 100 1k 10k 100k 1m LT1225 tpc11 10m 100m v s = ?5v
t a = 25? +psrr psrr voltage gain and phase vs frequency response vs frequency output swing vs settling time capacitive load settling time (ns) 0 output swing (v) 2 6 10 80 ? ? ?0 20 40 60 100 120 ltc1225 tpc14 0 4 8 ? ? v s = ?5
t a = 25?
10mv settling a v = 5 a v = 5 a v = 5 a v = 5 frequency (hz) 1m 4 voltage magnitude (db) 8 12 16 20 24 10m 100m v s = ?5v
t a = 25?
a v = 5 c = 100pf c = 0pf c = 50pf LT1225 tpc15 6 10 14 18 22 c = 1000pf
c = 500pf frequency (hz) 10k output impedance ( w ) 1 10 100m LT1225 tpc16
0.1 0.01 100k 1m 10m 100 v s = ?5v
t a = 25?
a v = 5 frequency (hz) 100 0 voltage gain (db) 20 40 60 80 100 1k 10k 100k 1m LT1225 tpc13 10m 100m 0 20 40 60 80 100 phase margin (deg) v s = ?5v v s = ?v t a = 25? v s = ?v v s = ?5v
LT1225 6 small signal, a v = 5 small signal, a v = C 5 u s a o pp l ic at i wu u i for atio the LT1225 may be inserted directly into ha2541, ha2544, ad847, el2020 and lm6361 applications, provided that the amplifier configuration is a noise gain of 5 or greater, and the nulling circuitry is removed. the suggested nulling circuit for the LT1225 is shown below. offset nulling the large-signal response in both inverting and noninvert- ing gain shows symmetrical slewing characteristics. nor- mally the noninverting response has a much faster rising edge than falling edge due to the rapid change in input common-mode voltage which affects the tail current of the input differential pair. slew enhancement circuitry has been added to the LT1225 so that the noninverting slew rate response is balanced. large signal, a v = 5 large signal, a v = C 5 input considerations resistors in series with the inputs are recommended for the LT1225 in applications where the differential input voltage exceeds 6v continuously or on a transient basis. an example would be in noninverting configurations with high input slew rates or when driving heavy capacitive loads. the use of balanced source resistance at each input is recommended for applications where dc accuracy must be maximized. capacitive loading the LT1225 is stable with all capacitive loads. this is accomplished by sensing the load induced output pole and adding compensation at the amplifier gain node. as the capacitive load increases, both the bandwidth and phase margin decrease so there will be peaking in the frequency layout and passive components as with any high speed operational amplifier, care must be taken in board layout in order to obtain maximum perfor- mance. key layout issues include: use of a ground plane, minimization of stray capacitance at the input pins, short lead lengths, rf-quality bypass capacitors located close to the device (typically 0.01 m f to 0.1 m f), and use of low esr bypass capacitors for high drive current applications (typically 1 m f to 10 m f tantalum). sockets should be avoided when maximum frequency performance is required, although low profile sockets can provide reasonable performance up to 50mhz. for more details see design note 50. feedback resistor values greater than 5k are not recommended because a pole is formed with the input capacitance which can cause peaking. if feedback resistors greater than 5k are used, a parallel capacitor of 5pf to 10pf should be used to cancel the input pole and optimize dynamic performance. transient response the LT1225 gain-bandwidth is 150mhz when measured at 1mhz. the actual frequency response in gain of 5 is considerably higher than 30mhz due to peaking caused by a second pole beyond the gain of 5 crossover point. this is reflected in the small-signal transient response. higher noise gain configurations exhibit less overshoot as seen in the inverting gain of 5 response. + 3 2 1 8 5k 0.1 m f 7 6 4 0.1 m f v + v LT1225 LT1225 ai01 LT1225 ai02 LT1225 ai03
7 LT1225 u s a o pp l ic at i wu u i for atio domain and in the transient response. the photo of the small-signal response with 1000pf load shows 50% peak- ing. the large-signal response with a 10,000pf load shows the output slew rate being limited by the short-circuit current. lag compensation wein bridge oscillator a v = C 5, c l = 1000pf a v = 5, c l = 10,000pf the LT1225 can drive coaxial cable directly, but for best pulse fidelity the cable should be doubly terminated with a resistor in series with the output. compensation the LT1225 has a typical gain-bandwidth product of 150mhz which allows it to have wide bandwidth in high gain configurations (i.e., in a gain of 10 it will have a bandwidth of about 15mhz). the amplifier is stable in a noise gain of 5 so the ratio of the output signal to the inverting input must be 1/5 or less. straightforward gain configurations of 5 or C4 are stable, but there are a few configurations that allow the amplifier to be stable for lower signal gains (the noise gain, however, remains 5 or more). one example is the summing amplifier shown in the typical applications section below. each input signal has a gain of Cr f /r in to the output, but it is easily seen that this configuration is equivalent to a gain of C4 as far as the amplifier is concerned. lag compensation can also be used to give a low frequency gain less than 5 with a high frequency gain of 5 or greater. the example below has a dc gain of one, but an ac gain of 5. the break frequency of the rc combination across the amplifier inputs should be approximately a factor of 10 less than the gain band- width of the amplifier divided by the high frequency gain (in this case 1/10 of 150mhz/5 or 3mhz). u s a o pp l ic at i ty p i ca l cable driving summing amplifier information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no represen- tation that the interconnection of circuits as described herein will not infringe on existing patent rights. LT1225 ai04 LT1225 ta04 r2
250 w in v out v r1
1k r3
75 w r4
75 w 75 cable w LT1225 + + 500 w LT1225 100pf v in v out 2k LT1225 ta03 a v = 1, f < 3mhz + LT1225 100pf v out
>10v p-p
1mhz LT1225 ta05 430 w 100pf 1.5k 1.5k #327
lamp + LT1225 v in1 v out r f LT1225 ta06 r in r in r in v in2 v in n r in = nr f
4
LT1225 8 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7487 (408) 432-1900 l fax : (408) 434-0507 l telex : 499-3977 w i spl ii f ed s w a ch e ti c lt1224 ?ta10 1 8 null bias 1 3 2 ?n +in bias 2 4 v 7 v+ 6 out u package d e sc r i pti o n8 package 8-lead plastic dip dimensions in inches (millimeters) unless otherwise noted. 1 2 3 4 0.150 ?0.157
(3.810 ?3.988) 8 7 6 5 0.189 ?0.197
(4.801 ?5.004) 0.228 ?0.244
(5.791 ?6.197) 0.010 ?0.020
(0.254 ?0.508) 0.016 ?0.050
0.406 ?1.270 45 0 8?typ 0.008 ?0.010
(0.203 ?0.254) so8 0392 0.053 ?0.069
(1.346 ?1.752) 0.014 ?0.019
(0.355 ?0.483) 0.004 ?0.010
(0.101 ?0.254) 0.050
(1.270)
bsc n8 0392 0.045 ?0.015
(1.143 ?0.381) 0.100 ?0.010
(2.540 ?0.254) 0.065
(1.651)
typ 0.045 ?0.065
(1.143 ?1.651) 0.130 ?0.005
(3.302 ?0.127) 0.020
(0.508)
min 0.018 ?0.003
(0.457 ?0.076) 0.125
(3.175)
min
0.009 ?0.015
(0.229 ?0.381) 0.300 ?0.320
(7.620 ?8.128) 0.325 +0.025
0.015 +0.635
0.381 8.255 () 12 3 4 87 6 5 0.250 ?0.010
(6.350 ?0.254)
0.400
(10.160)
max s8 package 8-lead plastic soic ? linear technology corporation 1992 lt/gp 1092 5k rev a
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