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| lt1991 1 1991ff C + 5v v in v m(in) v p(in) C + v out = v ref +v in swing 40mv to either rail r out <0.1 v ref = 2.5v input range C0.5v to 5.1v r in = 900k lt1991 1991 ta01 50k 50k 150k 150k 450k 450k 4pf 450k 450k 4pf typical application features applications description precision, 100? gain selectable ampli er the lt ? 1991 combines a precision operational ampli? er with eight precision resistors to form a one-chip solution for accurately amplifying voltages. gains from C13 to 14 with a gain accuracy of 0.04% can be achieved using no external components. the device is particularly well suited for use as a difference ampli? er, where the excellent resis- tor matching results in a common mode rejection ratio of greater than 75db. the ampli? er features a 50v maximum input offset volt- age and a gain bandwidth product of 560khz. the device operates from any supply voltage from 2.7v to 36v and draws only 100a supply current on a 5v supply. the output swings to within 40mv of either supply rail. the resistors have excellent matching, 0.04% over tem- perature for the 450k resistors. the matching temperature coef? cent is guaranteed less than 3ppm/c. the resistors are extremely linear with voltage, resulting in a gain non- linearity of less than 10ppm. the lt1991 is fully speci? ed at 5v and 15v supplies and from C40c to 125c. the device is available in space saving 10-lead msop and low pro? le (0.8mm) 3mm 3mm dfn packages. rail-to-rail gain = 1 difference ampli? er pin con? gurable as a difference ampli? er, inverting and noninverting ampli? er difference ampli? er gain range 1 to 13 cmrr >75db noninverting ampli? er gain range 0.07 to 14 inverting ampli? er gain range C0.08 to C13 gain error <0.04% gain drift < 3ppm/c wide supply range: single 2.7v to split 18v micropower: 100a supply current precision: 50v maximum input offset voltage 560khz gain bandwidth product rail-to-rail output space saving 10-lead msop and dfn packages handheld instrumentation medical instrumentation strain gauge ampli? ers differential to single-ended conversion resistor matching (%) percentage of units (%) 0.04 1991 ta01b C0.02 0 0.02 40 35 30 25 20 15 10 5 0 C0.04 450k resistors lt1991a distribution of resistor matching , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners.
lt1991 2 1991ff absolute maximum ratings total supply voltage (v + to v ? ) ................................40v input voltage (pins p1/m1, note 2) .......................60v input voltage (other inputs note 2) ..................v + + 0.2v to v ? ? 0.2v output short-circuit duration (note 3) ........... inde? nite operating temperature range (note 4) lt1991c ............................................... ?40c to 85c lt1991i ................................................ ?40c to 85c lt1991h ............................................ ?40c to 125c (note 1) top view dd package 10-lead (3mm 3mm) plastic dfn 10 9 6 7 8 4 5 3 2 1 m1 m3 m9 v cc out p1 p3 p9 v ee ref exposed pad connected to v ee pcb connection optional t jmax = 125c, lt1991 3 1991ff electrical characteristics symbol parameter conditions min typ max units g gain error v s = 15v, v out = 10v; r l = 10k g = 1; lt1991a g = 1; lt1991 g = 3 or 9; lt1991a g = 3 or 9; lt1991 0.04 0.08 0.06 0.12 % % % % gnl gain nonlinearity v s = 15v; v out = 10v; r l = 10k 110ppm g/t gain drift vs temperature (note 6) v s = 15v; v out = 10v; r l = 10k 0.3 3 ppm/c cmrr common mode rejection ratio, referred to inputs (rti) v s = 15v; v cm = 15.2v g = 9; lt1991a g = 3; lt1991a g = 1; lt1991a any gain; lt1991 80 75 75 60 100 93 90 70 db db db db v cm input voltage range (note 7) p1/m1 inputs v s = 15v; v ref = 0v v s = 5v, 0v; v ref = 2.5v v s = 3v, 0v; v ref = 1.25v C28 C0.5 0.75 27.6 5.1 2.35 v v v p1/m1 inputs, p9/m9 connected to ref v s = 15v; v ref = 0v v s = 5v, 0v; v ref = 2.5v v s = 3v, 0v; v ref = 1.25v C60 C14 C1.5 60 16.8 7.3 v v v p3/m3 inputs v s = 15v; v ref = 0v v s = 5v, 0v; v ref = 2.5v v s = 3v, 0v; v ref = 1.25v C15.2 0.5 0.95 15.2 4.2 1.95 v v v p9/m9 inputs v s = 15v; v ref = 0v v s = 5v, 0v; v ref = 2.5v v s = 3v, 0v; v ref = 1.25v C15.2 0.85 1.0 15.2 3.9 1.9 v v v v os op amp offset voltage (note 8) lt1991ams, v s = 5v, 0v 15 50 135 v v lt1991ams, v s = 15v 15 80 160 v v lt1991ms 25 100 200 v v lt1991dd 25 150 250 v v v os /t op amp offset voltage drift (note 6) 0.3 1 v/c ib op amp input bias current (note 11) 2.5 5 7.5 na na i os op amp input offset current (note 11) lt1991a 50 500 750 pa pa lt1991 50 1000 1500 pa pa op amp input noise voltage 0.01hz to 1hz 0.01hz to 1hz 0.1hz to 10hz 0.1hz to 10hz 0.35 0.07 0.25 0.05 v p-p v rms v p-p v rms e n input noise voltage density g = 1; f = 1khz g = 9; f = 1khz 180 46 nv/ h z nv/ h z the denotes the speci? cations which apply over the operating temperature range of 0c to 70c for c-grade parts and C40c to 85c for i-grade parts, otherwise speci? cations are at t a = 25c. difference ampli? er con? guration, v s = 5v, 0v or 15v; v cm = v ref = half supply, unless otherwise noted. lt1991 4 1991ff symbol parameter conditions min typ max units r in input impedance (note 10) p1 (m1 = ground) p3 (m3 = ground) p9 (m9 = ground) 630 420 350 900 600 500 1170 780 650 k k k m1 (p1 = ground) m3 (p3 = ground) m9 (p9 = ground) 315 105 35 450 150 50 585 195 65 k k k r resistor matching (note 9) 450k resistors, lt1991a other resistors, lt1991a 450k resistors, lt1991 other resistors, lt1991 0.01 0.02 0.02 0.04 0.04 0.06 0.08 0.12 % % % % r/t resistor temperature coef? cient (note 6) resistor matching absolute value 0.3 C30 3 ppm/c ppm/c psrr power supply rejection ratio v s = 1.35v to 18v (note 8) 105 135 db minimum supply voltage 2.4 2.7 v v out output voltage swing (to either rail) no load v s = 5v, 0v v s = 5v, 0v v s = 15v 40 55 65 110 mv mv mv 1ma load v s = 5v, 0v v s = 5v, 0v v s = 15v 150 225 275 300 mv mv mv i sc output short-circuit current (sourcing) drive output positive; short output to ground 8 4 12 ma ma output short-circuit current (sinking) drive output negative; short output to v s or midsupply 8 4 21 ma ma bw C3db bandwidth g = 1 g = 3 g = 9 110 78 40 khz khz khz gbwp op amp gain bandwidth product f = 10khz 560 khz t r , t f rise time, fall time g = 1; 0.1v step; 10% to 90% g = 9; 0.1v step; 10% to 90% 3 8 s s t s settling time to 0.01% g = 1; v s = 5v, 0v; 2v step g = 1; v s = 5v, 0v; C2v step g = 1; v s = 15v, 10v step g = 1; v s = 15v, C10v step 42 48 114 74 s s s s sr slew rate v s = 5v, 0v; v out = 1v to 4v v s = 15v; v out = 10v; v meas = 5v 0.06 0.08 0.12 0.12 v/s v/s i s supply current v s = 5v, 0v 100 110 150 a a v s = 15v 130 160 210 a a electrical characteristics the denotes the speci? cations which apply over the operating temperature range of 0c to 70c for c-grade parts and C40c to 85c for i-grade parts, otherwise speci? cations are at t a = 25c. difference ampli? er con? guration, v s = 5v, 0v or 15v; v cm = v ref = half supply, unless otherwise noted. lt1991 5 1991ff electrical characteristics symbol parameter conditions min typ max units g gain error v s = 15v, v out = 10v; r l = 10k g = 1 g = 3 or 9 0.08 0.12 % % gnl gain nonlinearity v s = 15v; v out = 10v; r l = 10k 110ppm g/t gain drift vs temperature (note 6) v s = 15v; v out = 10v; r l = 10k 0.3 3 ppm/c cmrr common mode rejection ratio, referred to inputs (rti) v s = 15v; v cm = 15.2v g = 9 g = 3 g = 1 77 70 70 100 93 90 db db db v cm input voltage range (note 7) p1/m1 inputs v s = 15v; v ref = 0v v s = 5v, 0v; v ref = 2.5v v s = 3v, 0v; v ref = 1.25v C28 C0.5 0.75 27.6 5.1 2.35 v v v p1/m1 inputs, p9/m9 connected to ref v s = 15v; v ref = 0v v s = 5v, 0v; v ref = 2.5v v s = 3v, 0v; v ref = 1.25v C60 C14 C1.5 60 16.8 7.3 v v v p3/m3 inputs v s = 15v; v ref = 0v v s = 5v, 0v; v ref = 2.5v v s = 3v, 0v; v ref = 1.25v C15.2 0.5 0.95 15.2 4.2 1.95 v v v p9/m9 inputs v s = 15v; v ref = 0v v s = 5v, 0v; v ref = 2.5v v s = 3v, 0v; v ref = 1.25v C15.2 0.85 1.0 15.2 3.9 1.9 v v v v os op amp offset voltage (note 8) lt1991ms 25 100 285 v v lt1991dd 25 150 295 v v v os /t op amp offset voltage drift (note 6) 0.3 1 v/c ib op amp input bias current (note 11) 2.5 5 25 na na i os op amp input offset current (note 11) 50 1000 4500 pa pa op amp input noise voltage 0.01hz to 1hz 0.01hz to 1hz 0.1hz to 10hz 0.1hz to 10hz 0.35 0.07 0.25 0.05 v p-p v rms v p-p v rms e n input noise voltage density g = 1; f = 1khz g = 9; f = 1khz 180 46 nv/ h z nv/ h z r in input impedance (note 10) p1 (m1 = ground) p3 (m3 = ground) p9 (m9 = ground) 630 420 350 900 600 500 1170 780 650 k k k m1 (p1 = ground) m3 (p3 = ground) m9 (p9 = ground) 315 105 35 450 150 50 585 195 65 k k k r resistor matching (note 9) 450k resistors other resistors 0.02 0.04 0.08 0.12 % % r/t resistor temperature coef? cient (note 6) resistor matching absolute value 0.3 C30 3 ppm/c ppm/c the denotes the speci? cations which apply over the operating temperature range of C40c to 125c for h-grade parts, otherwise speci? cations are at t a = 25c. difference ampli? er con? guration, v s = 5v, 0v or 15v; v cm = v ref = half supply, unless otherwise noted. lt1991 6 1991ff symbol parameter conditions min typ max units psrr power supply rejection ratio v s = 1.35v to 18v (note 8) 105 135 db minimum supply voltage 2.4 2.7 v v out output voltage swing (to either rail) no load v s = 5v, 0v v s = 5v, 0v v s = 15v 40 55 75 120 mv mv mv 1ma load v s = 5v, 0v v s = 5v, 0v v s = 15v 150 225 300 340 mv mv mv i sc output short-circuit current (sourcing) drive output positive; short output to ground 8 4 12 ma ma output short-circuit current (sinking) drive output negative; short output to v s or midsupply 8 4 21 ma ma bw C3db bandwidth g = 1 g = 3 g = 9 110 78 40 khz khz khz gbwp op amp gain bandwidth product f = 10khz 560 khz t r , t f rise time, fall time g = 1; 0.1v step; 10% to 90% g = 9; 0.1v step; 10% to 90% 3 8 s s t s settling time to 0.01% g = 1; v s = 5v, 0v; 2v step g = 1; v s = 5v, 0v; C2v step g = 1; v s = 15v, 10v step g = 1; v s = 15v, C10v step 42 48 114 74 s s s s sr slew rate v s = 5v, 0v; v out = 1v to 4v v s = 15v; v out = 10v; v meas = 5v 0.06 0.08 0.12 0.12 v/s v/s i s supply current v s = 5v, 0v 100 110 180 a a v s = 15v 130 160 250 a a electrical characteristics the denotes the speci? cations which apply over the operating temperature range of C40c to 125c for h-grade parts, otherwise speci? cations are at t a = 25c. difference ampli? er con? guration, v s = 5v, 0v or 15v; v cm = v ref = half supply, unless otherwise noted. note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: the p3/m3 and p9/m9 inputs should not be taken more than 0.2v beyond the supply rails. the p1/m1 inputs can withstand 60v if p9/m9 are grounded and v s = 15v (see applications information section about high voltage cm difference ampli? ers). note 3 : a heat sink may be required to keep the junction temperature below absolute maximum ratings. note 4 : both the lt1991c and lt1991i are guaranteed functional over the C40c to 85c temperature range. the ltc1991h is guaranteed functional over the C40c to 125c temperature range. note 5: the lt1991c is guaranteed to meet the speci? ed performance from 0c to 70c and is designed, characterized and expected to meet speci? ed performance from C40c to 85c but is not tested or qa sampled at these temperatures. the lt1991i is guaranteed to meet speci? ed performance from C40c to 85c. the lt1991h is guaranteed to meet speci? ed performance from C40c to 125c. note 6: this parameter is not 100% tested. note 7: input voltage range is guaranteed by the cmrr test at v s = 15v. for the other voltages, this parameter is guaranteed by design and through correlation with the 15v test. see the applications information section to determine the valid input voltage range under various operating conditions. note 8: offset voltage, offset voltage drift and psrr are de? ned as referred to the internal op amp. you can calculate output offset as follows. in the case of balanced source resistance, v os,out = v os ? noisegain + i os ? 450k + i b ? 450k ? (1C r p /r n ) where r p and r n are the total resistance at the op amp positive and negative terminal respectively. note 9: applies to resistors that are connected to the inverting inputs. resistor matching is not tested directly, but is guaranteed by the gain error test. note 10: input impedance is tested by a combination of direct measurements and correlation to the cmrr and gain error tests. note 11: i b and i os are tested at v s = 5v, 0v only. lt1991 7 1991ff supply voltage (v) 0 supply current (a) 200 175 150 125 100 75 50 25 0 16 1991 g01 4 2 6 10 14 18 8 12 20 t a = 85c t a = C40c t a = 25c temperature (c) C50 output voltage swing (mv) 100 1991 g02 050 60 40 20 v ee C25 25 75 125 v s = 5v, 0v no load output high (right axis) output low (left axis) v cc C20 C40 C60 load current (ma) 0 output voltage (mv) 1400 1200 1000 800 600 400 200 v ee 1 99 1 g03 2 10 9 8 7 6 5 1 34 v s = 5v, 0v t a = 85c t a = C40c t a = 25c load current (ma) v cc C100 C200 C300 C400 C500 C600 C700 C800 C900 C1000 output voltage swing (mv) 1991 g04 0123 4 5 67 8910 v s = 5v, 0v t a = 85c t a = C40c t a = 25c temperature (c) C50 output short-circuit current (ma) 25 20 15 10 5 0 0 50 75 1991 g05 C25 25 100 125 v s = 5v, 0v sinking sourcing gain (v/v) 1 input offset voltage (v) 150 100 50 0 C50 C100 C150 12 91011 13 5 1991 g06 23 8 7 6 4 v s = 5v, 0v representative parts gain (v/v) 1 output offset voltage (v) 1000 750 500 250 0 C250 C500 C750 C1000 12 91011 13 5 1991 g07 23 8 7 6 4 v s = 5v, 0v representative parts load current (ma) 0 gain error (%) 3 5 1991 g08 12 4 0.04 0.03 0.02 0.01 0 C0.01 C0.02 C0.03 C0.04 gain = 1 v s = 15v v out = 10v t a = 25c representative units temperature (c) C50 slew rate (v/s) 0.30 0.25 0.20 0.15 0.10 0.05 0 25 75 1991 g09 C25 0 50 100 125 gain = 1 v s = 15v v out = 10v sr C (falling edge) sr + (rising edge) typical performance characteristics supply current vs supply voltage output voltage swing vs temperature output voltage swing vs load current (output low) output voltage swing vs load current (output high) output short-circuit current vs temperature input offset voltage vs difference gain output offset voltage vs difference gain gain error vs load current slew rate vs temperature (difference ampli? er con? guration) lt1991 8 1991ff gain setting (v/v) 1 C3db bandwidth (khz) 120 100 80 60 40 20 0 35 79 1991 g10 11 13 2 4 6 8 10 12 v s = 5v, 0v t a = 25c bandwidth vs gain cmrr vs frequency psrr vs frequency output impedance vs frequency cmrr vs temperature gain error vs temperature gain vs frequency gain and phase vs frequency 0.01hz to 1hz voltage noise (difference ampli? er con? guration) frequency (hz) cmrr (db) 120 110 100 90 80 70 60 50 40 30 20 10 0 10 1k 10k 1m 1991 g11 100 100k v s = 5v, 0v t a = 25c gain = 9 gain = 1 gain = 3 psrr (db) 120 110 100 90 80 70 60 50 40 30 20 10 0 v s = 5v, 0v t a = 25c gain = 9 gain = 1 gain = 3 frequency (hz) 10 1k 10k 1991 g12 100 100 k frequency (hz) output impedance () 1 100 1k 100 k 10k 1991 g13 10 1000 100 10 1 0.1 0.01 v s = 5v, 0v t a = 25c gain = 9 gain = 1 gain = 3 temperature (c) C50 cmrr (db) 120 100 80 60 40 20 0 25 75 1991 g14 C25 0 50 100 125 gain = 1 v s = 15v representative units temperature (c) C50 gain error (%) 0.030 0.025 0.020 0.015 0.010 0.005 0 25 75 1991 g15 C25 0 50 100 125 gain = 1 v s = 15v representative units frequency (khz) 1 gain (db) 30 20 10 0 C10 C20 10 100 60 0 1991 g16 gain = 9 gain = 3 gain = 1 v s = 5v, 0v t a = 25c frequency (khz) 1 gain (db) phase (deg) 2 1 0 C1 C2 C3 C4 C5 C6 C7 C8 0 C45 C90 C135 C180 10 100 400 1991 g17 0.5 v s = 5v, 0v t a = 25c gain = 1 phase gain v s = 15v t a = 25c measured in g =13 referred to op amp inputs 0 10 2030405060708090100 time (s) op amp voltage noise (100nv/div) 1991 g21 typical performance characteristics lt1991 9 1991ff typical performance characteristics block diagram pin functions p1 (pin 1): noninverting gain-of-1 input. connects a 450k internal resistor to the op amps noninverting input. p3 (pin 2): noninverting gain-of-3 input. connects a 150k internal resistor to the op amps noninverting input. p9 (pin 3): noninverting gain-of-9 input. connects a 50k internal resistor to the op amps noninverting input. v ee (pin 4): negative power supply. can be either ground (in single supply applications), or a negative voltage (in split supply applications). ref (pin 5): reference input. sets the output level when difference between inputs is zero. connects a 450k internal resistor to the op amps noninverting input. out (pin 6): output. v out = v ref + 1 ? (v p1 C v m1 ) + 3 ? (v p3 C v m3 ) + 9 ? (v p9 C v m9 ). v cc (pin 7): positive power supply. can be anything from 2.7v to 36v above the v ee voltage. m9 (pin 8): inverting gain-of-9 input. connects a 50k internal resistor to the op amps inverting input. m3 (pin 9): inverting gain-of-3 input. connects a 150k internal resistor to the op amps inverting input. m1 (pin 10): inverting gain-of-1 input. connects a 450k internal resistor to the op amps inverting input. exposed pad: must be soldered to pcb. (difference ampli? er con? guration) 50mv/div 5s/div gain = 1 1991 g18 50mv/div 5s/div 1991 g19 gain = 3 50mv/div 5s/div gain = 9 1991 g20 bandwidth vs gain cmrr vs frequency psrr vs frequency lt1991 1991 bd 9 8 2 3 4 5 7 6 10 1 m1 m3 m9 p1 p3 p9 v cc v ee out ref 50k 50k 150k 150k 450k 450k 450k 450k inm inp out 4pf 4pf lt1991 10 1991ff introduction the lt1991 may be the last op amp you ever have to stock. because it provides you with several precision matched resistors, you can easily con? gure it into several different classical gain circuits without adding external components. the several pages of simple circuits in this data sheet demonstrate just how easy the lt1991 is to use. it can be con? gured into difference ampli? ers, as well as into inverting and noninverting single ended ampli? ers. the fact that the resistors and op amp are provided together in such a small package will often save you board space and reduce complexity for easy probing. the op amp the op amp internal to the lt1991 is a precision device with 15v typical offset voltage and 3na input bias current. the input offset current is extremely low, so matching the source resistance seen by the op amp inputs will provide for the best output accuracy. the op amp inputs are not rail-to-rail, but extend to within 1.2v of v cc and 1v of v ee . for many con? gurations though, the chip inputs will function rail-to-rail because of effective attenuation to the +input. the output is truly rail-to-rail, getting to within 40mv of the supply rails. the gain bandwidth product of the op amp is about 560khz. in noise gains of 2 or more, it is stable into capacitive loads up to 500pf. in noise gains below 2, it is stable into capacitive loads up to 100pf. the resistors the resistors internal to the lt1991 are very well matched sichrome based elements protected with barrier metal. although their absolute tolerance is fairly poor (30%), their matching is to within 0.04%. this allows the chip to achieve a cmrr of 75db, and gain errors within 0.04%. the resistor values are 50k, 150k, and 2 of 450k, con- nected to each of the inputs. the resistors have power limitations of 1watt for the 450k resistors, 0.3watt for the 150k resistors and 0.5watt for the 50k resistors; however, in practice, power dissipation will be limited well below these values by the maximum voltage allowed on the input and ref pins. the 450k resistors connected to the m1 and p1 inputs are isolated from the substrate, and can therefore be taken beyond the supply voltages. the naming of the pins p1, p3, p9, etc., is based on their relative admittances. because it has 9 times the admittance, the voltage applied to the p9 input has 9 times the effect of the voltage applied to the p1 input. bandwidth the bandwidth of the lt1991 will depend on the gain you select (or more accurately the noise gain resulting from the gain you select). in the lowest con? gurable gain of 1, the C3db bandwidth is limited to 450khz, with peaking of about 2db at 280khz. in the highest con? gurable gains, bandwidth is limited to 32khz. input noise the lt1991 input noise is dominated by the johnson noise of the internal resistors ( 4 k t r). paralleling all four resistors to the +input gives a 32.1k resistance, for 23nv/ h z of voltage noise. the equivalent network on the Cinput gives another 23nv/ h z , and taking their rms sum gives a total 33nv/ h z input referred noise ? oor. output noise depends on con? guration and noise gain. input resistance the lt1991 input resistances vary with con? guration, but once con? gured are apparent on inspection. note that resistors connected to the op amps Cinput are looking into a virtual ground, so they simply parallel. any feedback resistance around the op amp does not contribute to input resistance. resistors connected to the op amps +input are looking into a high impedance, so they add as paral- lel or series depending on how they are connected, and whether or not some of them are grounded. the op amp +input itself presents a very high g impedance. in the classical noninverting op amp con? guration, the lt1991 presents the high input impedance of the op amp, as is usual for the noninverting case. common mode input voltage range the lt1991 valid common mode input range is limited by three factors: 1. maximum allowed voltage on the pins 2. the input voltage range of the internal op amp 3. valid output voltage applications information lt1991 11 1991ff the maximum voltage allowed on the p3, m3, p9, and m9 inputs includes the positive and negative supply plus a diode drop. these pins should not be driven more than 0.2v outside of the supply rails. this is because they are connected through diodes to internal manufacturing post- package trim circuitry, and through a substrate diode to v ee . if more than 10ma is allowed to ? ow through these pins, there is a risk that the lt1991 will be detrimmed or damaged. the p1 and m1 inputs do not have clamp diodes or substrate diodes or trim circuitry and can be taken well outside the supply rails. the maximum allowed voltage on the p1 and m1 pins is 60v. the input voltage range of the internal op amp extends to within 1.2v of v cc and 1v of v ee . the voltage at which the op amp inputs common mode is determined by the voltage at the op amps +input, and this is determined by the voltages on pins p1, p3, p9 and ref (see calculating input voltage range section). this is true provided that the op amp is functioning and feedback is maintaining the inputs at the same voltage, which brings us to the third requirement. for valid circuit function, the op amp output must not be clipped. the output will clip if the input signals are attempt- ing to force it to within 40mv of its supply voltages. this usually happens due to too large a signal level, but it can also occur with zero input differential and must therefore be included as an example of a common mode problem. consider figure 1. this shows the lt1991 con? gured as a gain of 13 difference ampli? er on a single supply with the output ref connected to ground. this is a great circuit, but it does not support v dm = 0v at any common mode because the output clips into ground while trying to produce 0v out . it can be ? xed simply by declaring the valid input differential range not to extend below +4mv, or by elevating the ref pin above 40mv, or by providing a negative supply. calculating input voltage range figure 2 shows the lt1991 in the generalized case of a difference ampli? er, with the inputs shorted for the common mode calculation. the values of r f and r g are dictated by how the p inputs and ref pin are connected. by superposition we can write: v int = v ext ? (r f /(r f + r g )) + v ref ? (r g /(r f + r g )) or, solving for v ext : v ext = v int ? (1 + r g /r f ) C v ref ? r g /r f but valid v int voltages are limited to v cc C 1.2v and v ee + 1v, so: max v ext = (v cc C 1.2) ? (1 + r g /r f ) C v ref ? r g /r f and: min v ext = (v ee + 1) ? (1 + r g /r f ) C v ref ? r g /r f these two voltages represent the high and low extremes of the common mode input range, if the other limits have not already been exceeded (1 and 3, above). in most cases, the inverting inputs m1 through m9 can be taken further than these two extremes because doing this does not move the op amp input common mode. to calculate the limit on this additional range, see figure 3. note that, C + 1991 f01 50k 150k 450k 50k 150k 450k 450k 450k ref 5v v cm 2.5v v dm 0v C + 8 7 6 5 4 9 10 1 2 3 lt1991 v out = 13 ? v dm 4pf 4pf C + v ref r f r f r g r g 1991 f02 v ext v int v cc v ee figure 1. difference ampli? er cannot produce 0v on a single supply. provide a negative supply, or raise pin 5, or provide 4mv of v dm figure 2. calculating cm input voltage range applications information lt1991 12 1991ff with v more = 0, the op amp output is at v ref . from the max v ext (the high cm limit), as v more goes positive, the op amp output will go more negative from v ref by the amount v more ? r f /r g , so: v out = v ref C v more ? r f /r g or: v more = (v ref C v out ) ? r g /r f the most negative that v out can go is v ee + 0.04v, so: max v more = (v ref C v ee C 0.04v) ? r g /r f (should be positive) the situation where this function is negative, and there- fore problematic, when v ref = 0 and v ee = 0, has already been dealt with in figure 1. the strength of the equation is demonstrated in that it provides the three solutions suggested in figure 1: raise v ref , lower v ee , or provide some negative v more . likewise, from the lower common mode extreme, mak- ing the negative input more negative will raise the output voltage, limited by v cc C 0.04v. min v more = (v ref C v cc + 0.04v) ? r g /r f (should be negative) again, the additional input range calculated here is only available provided the other remaining constraint is not violated, the maximum voltage allowed on the pin. the classical noninverting ampli? er: high input z perhaps the most common op amp con? guration is the noninverting ampli? er. figure 4 shows the textbook representation of the circuit on the top. the lt1991 is shown on the bottom con? gured in a precision gain of 5.5. one of the bene? ts of the noninverting op amp con? gura- tion is that the input impedance is extremely high. the lt1991 maintains this bene? t. given the ? nite number of available feedback resistors in the lt1991, the number of gain con? gurations is also ? nite. the complete list of such hi-z input noninverting gain con? gurations is shown in table 1. many of these are also represented in figure 5 in schematic form. note that the p-side resistor inputs have been connected so as to match the source impedance seen by the internal op amp inputs. note also that gain and noise gain are identical, for optimal precision. C + v ref r f r f r g r g 1991 f03 v ext max or min v int v more v cc v ee C + r f r g v in v in v out v out v out = gain ? v in gain = 1 + r f /r g C + 1991 f04 50k 150k 450k 50k 150k 450k 450k 450k 8 6 5 9 10 1 2 3 lt1991 classical noninverting op amp configuration. you provide the resistors. classical noninverting op amp configuration implemented with lt1991. r f = 225k, r g = 50k, gain = 5.5. gain is achieved by grounding, floating or feeding back the available resistors to arrive at desired r f and r g . we provide you with <0.1% resistors. 4pf 4pf figure 3. calculating additional voltage range of inverting inputs figure 4. the lt1991 as a classical noninverting op amp applications information lt1991 13 1991ff table 1. con? guring the m pins for simple noninverting gains. the p inputs are driven as shown in the examples on the next page. m9, m3, m1 connection gain m9 m3 m1 1 output output output 1.077 output output ground 1.1 output float ground 1.25 float output ground 1.273 output ground output 1.3 output ground float 1.4 output ground ground 2 float float ground 2.5 float ground output 2.8 ground output output 3.25 ground output float 3.5 ground output ground 4 float ground float 5 float ground ground 5.5 ground float output 7 ground ground output 10 ground float float 11 ground float ground 13 ground ground float 14 ground ground ground applications information lt1991 14 1991ff v s C v s C v s + 1991 f05 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 v in v in v in out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 gain = 1 gain = 2 gain = 3.25 gain = 4 gain = 5 gain = 5.5 gain = 7 gain = 10 gain = 13 gain = 14 gain = 11 figure 5. some implementations of classical noninverting gains using the lt1991. high input z is maintained. applications information lt1991 15 1991ff v in okay up to 60v + 50k 150k 450k 450k 5 1 2 3 lt1991 attenuating to the +input by driving and grounding and floating inputs r a = 450k, r g = 50k, so a = 0.1. v int v int v int = a ? v in a = r g /(r a + r g ) v in lt1991 r a r g 1991 f06 classical attenuator 4pf attenuation using the p input resistors attenuation happens as a matter of fact in difference ampli? er con? gurations, but it is also used for reducing peak signal level or improving input common mode range even in single ended systems. when signal conditioning indicates a need for attenuation, the lt1991 resistors are ready at hand. the four precision resistors can provide several attenuation levels, and these are tabulated in table 2 as a design reference. because the attenuations and the noninverting gains are set independently, they can be combined. this provides high gain resolution, about 340 unique gains between 0.077 and 14, as plotted in figure 7. this is too large a number to tabulate, but the designer can calculate achievable gain by taking the vector product of the gains and attenuations in tables 1 and 2, and seeking the best match. average gain resolution is 1.5%, with a worst-case of 7%. figure 6. lt1991 provides for easy attenuation to the op amps +input. the p1 input can be taken well outside of the supplies. figure 7. over 346 unique gain settings achievable with the lt1991 by combining attenuation with noninverting gain count 0 100 10 1 0.1 0.01 150 1991 f07 50 100 200 250 350 300 gain t able 2. con? guring the p pins for various attenuations. those shown in bold are functional even when the input drive exceeds the supplies. p9, p3, p1, ref connection a p9p3p1ref 0.0714 ground ground drive ground 0.0769 ground ground drive float 0.0909 ground float drive ground 0.1 ground float drive float 0.143 ground ground drive drive 0.182 ground float drive drive 0.2 float ground drive ground 0.214 ground drive ground ground 0.231 ground drive float ground 0.25 float ground drive float 0.286 ground drive drive ground 0.308 ground drive drive float 0.357 ground drive drive drive 0.4 float ground drive drive 0.5 float float drive ground 0.6 float drive ground ground 0.643 drive ground ground ground 0.692 drive ground float ground 0.714 drive ground drive ground 0.75 float drive float ground 0.769 drive ground drive float 0.786 drive ground drive drive 0.8 float drive drive ground 0.818 drive float ground ground 0.857 drive drive ground ground 0.9 drive float float ground 0.909 drive float drive ground 0.923 drive drive float ground 0.929 drive drive drive ground 1 drive drive drive drive applications information lt1991 16 1991ff inverting con? guration the inverting ampli? er, shown in figure 8, is another classical op amp con? guration. the circuit is actually identical to the noninverting ampli? er of figure 4, except that v in and gnd have been swapped. the list of avail- able gains is shown in table 3, and some of the circuits are shown in figure 9. noise gain is 1+|gain|, as is the usual case for inverting ampli? ers. again, for the best dc performance, match the source impedance seen by the op amp inputs. C + r f r g v in v in (drive) v out v out v out = gain ? v in gain = C r f /r g C + 1991 f08 50k 150k 450k 50k 150k 450k 450k 450k 8 6 5 9 10 1 2 3 lt1991 classical inverting op amp configuration. you provide the resistors. classical inverting op amp configuration implemented with lt1991. r f = 225k, r g = 50k, gain = C4.5. gain is achieved by grounding, floating or feeding back the available resistors to arrive at desired r f and r g . we provide you with <0.1% resistors. 4pf 4pf figure 8. the lt1991 as a classical inverting op amp. note the circuit is identical to the noninverting ampli? er, except that v in and ground have been swapped. table 3. con? guring the m pins for simple inverting gains m9, m3, m1 connection gain m9 m3 m1 C0.077 output output drive C0.1 output float drive C0.25 float output drive C0.273 output drive output C0.3 output drive float C0.4 output drive drive C1 float float drive C1.5 float drive output C1.8 drive output output C2.25 drive output float C2.5 drive output drive C3 float drive float C4 float drive drive C4.5 drive float output C6 drive drive output C9 drive float float C10 drive float drive C12 drive drive float C13 drive drive drive applications information lt1991 17 1991ff 4 v s C 4 v s C v s + 1991 f09 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee v s C v s + v s C v s + v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + ref lt1991 8 9 10 1 2 3 7 6 5 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 v in v in v in out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 m9 m3 m1 p1 p3 p9 out v cc v out v in v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 gain = C0.25 gain = C1 gain = C2.25 gain = C3 gain = C4 gain = C4.5 gain = C6 gain = C9 gain = C12 gain = C13 gain = C10 figure 9. it is simple to get precision inverting gains with the lt1991. input impedance varies from 45k (gain = C13) to 450k (gain = C1). applications information lt1991 18 1991ff difference ampli? ers the resistors in the lt1991 allow it to easily make differ- ence ampli? ers also. figure 10 shows the basic 4-resistor difference ampli? er and the lt1991. a difference gain of 3 is shown, but notice the effect of the additional dashed connections. by connecting the 450k resistors in paral- lel, the gain is reduced by a factor of 2. of course, with so many resistors, there are many possible gains. table 4 shows the difference gains and how they are achieved. note that, as for inverting ampli? ers, the noise gain is 1 more than the signal gain. C + r f r g r g v in + v in + v in C v in C v out v out v out = gain ? (v in + C v in C ) gain = r f /r g C + 1991 f1 0 50k 150k 450k 50k 150k 450k 450k 450k 8 6 5 9 10 1 2 3 lt1991 classical difference amplifier using the lt1991 classical difference amplifier implemented with lt1991. r f = 450k, r g = 150k, gain = 3. adding the dashed connections connects the two 450k resistors in parallel, so r f is reduced to 225k. gain becomes 225k/150k = 1.5. r f parallel to change r f , r g m9 m3 m1 p1 p3 p9 4pf 4pf figure 10. difference ampli? er using the lt1991. gain is set simply by connecting the correct resistors or combinations of resistors. gain of 3 is shown, with dashed lines modifying it to gain of 1.5. noise gain is optimal. table 4. connections giving difference gains for the lt1991 gain v in + v in C output gnd (ref) 0.077 p1 m1 m3, m9 p3, p9 0.1 p1 m1 m9 p9 0.25 p1 m1 m3 p3 0.273 p3 m3 m1, m9 p1, p9 0.3 p3 m3 m9 p9 0.4 p1, p3 m1, m3 m9 p9 1 p1 m1 1.5 p3 m3 m1 p1 1.8 p9 m9 m1, m3 p1, p3 2.25 p9 m9 m3 p3 2.5 p1, p9 m1, m9 m3 p3 3p3m3 4 p1, p3 m1, m3 4.5 p9 m9 m1 p1 6 p3, p9 m3, m9 m1 p1 9p9m9 10 p1, p9 m1, m9 12 p3, p9 m3, m9 13 p1, p3, p9 m1, m3, m9 applications information lt1991 19 1991ff figure 11. many difference gains are achievable just by strapping the pins v s C v s + 1991 f11 m9 m3 m1 p1 p3 p9 out v cc v out v ee v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + v s C v s + ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 gain = 0.25 gain = 1 gain = 2.25 gain = 3 gain = 4 gain = 4.5 gain = 6 gain = 9 gain = 12 gain = 13 gain = 10 v in + v in C v in + v in + v in + v in C v in + v in C v in + v in C v in + v in C v in + v in C v in + v in C v in + v in C v in + v in C v in C v in C applications information lt1991 20 1991ff 1991 f13 v s C v s + v s C v s + v s C v s + v s C v s + m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 gain = 2 gain = 5 gain = 7 gain = 8 gain = 11 v in + v in C v in + v in C v in + v in C v in + v in C v s C v s + m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 v in + v in C C + r f r g r g v in + v in + v in C v in C v out v out v out = gain ? (v in + C v in C ) gain = r f /r g C + 1991 f12 50k 150k 450k 50k 150k 450k 450k 450k 8 6 5 9 10 1 2 3 lt1991 classical difference amplifier classical difference amplifier implemented with lt1991. r f = 450k, r g = 150k, gain = 3. gain can be adjusted by "cross coupling." making the dashed connections reduce the gain from 3 t0 2. when cross coupling, see what is connected to the v in + voltage. connecting p3 and m1 gives +3 C1 = 2. connections to v in C are symmetric: m3 and p1. r f cross- coupling m9 m3 m1 p1 p3 p9 4pf 4pf difference ampli? er: additional integer gains using cross-coupling figure 12 shows the basic difference ampli? er as well as the lt1991 in a difference gain of 3. but notice the effect of the additional dashed connections. this is referred to as cross-coupling and has the effect of reducing the differential gain from 3 to 2. using this method, additional integer gains are achievable, as shown in table 5 below, so that all integer gains from 1 to 13 are achieved with the lt1991. note that the equations can be written by inspection from the v in + connections, and that the v in C connections are simply the opposite (swap p for m and m for p). noise gain, bandwidth, and input impedance speci? cations for the various cases are also tabulated, as these are not obvious. schematics are provided in figure 13. figure 13. integer gain difference ampli? ers using cross-coupling figure 12. another method of selecting difference gain is cross-coupling. the additional method means the lt1991 provides all integer gains from 1 to 13. table 5. connections using cross-coupling. note that equations can be written by inspection of the v in + column gain v in + v in C equation noise gain C3db bw khz r in + typ k r in C typ k 2 p3, m1 m3, p1 3 C 1 5 70 281 141 5 p9, m3, m1 m9, p3, p1 9 C 3 C 1 14 32 97 49 6* p9, m3 m9, p3 9 C 3 13 35 122 49 7 p9, p1, m3 m9, m1, p3 9 + 1 C 3 14 32 121 44 8 p9, m1 m9, p1 9 C 1 11 38 248 50 11 p9, p3, m1 m9, m3, p1 9 + 3 C 1 14 32 242 37 *gain of 6 is better implemented as shown previously, but is included here for completeness. applications information lt1991 21 1991ff high voltage cm difference ampli? ers this class of difference ampli? er remains to be discussed. figure 14 shows the basic circuit on the top. the effective input voltage range of the circuit is extended by the fact that resistors r t attenuate the common mode voltage seen by the op amp inputs. for the lt1991, the most useful resistors for r g are the m1 and p1 450k resistors, be- cause they do not have diode clamps to the supplies and therefore can be taken outside the supplies. as before, the input cm of the op amp is the limiting factor and is set by the voltage at the op amp +input, v int . by superposition we can write: v int = v ext ? (r f ||r t )/(r g + r f ||r t ) + v ref ? (r g ||r t )/ (r f + r g ||r t ) + v term ? (r f ||r g )/(r t + r f ||r g ) solving for v ext : v ext = (1 + r g /(r f ||r t )) ? (v int C v ref ? (r g ||r t )/ (r f + r g ||r t ) C v term ? (r f ||r g )/(r t + r f ||r g )) given the values of the resistors in the lt1991, this equa- tion has been simpli? ed and evaluated, and the resulting equations provided in table 6. as before, substituting v cc C 1.2 and v ee + 1 for v lim will give the valid upper and lower common mode extremes respectively. following are sample calculations for the case shown in figure 14, right-hand side. note that p9 and m9 are terminated so row 3 of table 6 provides the equation: max v ext = 11 ? (v cc C 1.2v) C v ref C 9 ? v term = 11 ? (10.8v) C 2.5 C 9 ? 12 = 8.3v and: min v ext = 11 ? (v ee + 1v) C v ref C 9 ? v term = 11 ? (1v) C 2.5 C 9 ? 12 = C99.5v but this exceeds the 60v absolute maximum rating of the p1, m1 pins, so C60v becomes the de facto nega- tive common mode limit. several more examples of high cm circuits are shown in figures 15, 16, 17 for various supplies. C + r f r g r g v in + (= v ext ) v in + v in C v in C v out v out v out = gain ? (v in + C v in C ) gain = r f /r g C + 1991 f14 50k 150k 450k 50k 150k 450k 450k 450k 8 7 4 6 5 9 10 1 2 3 lt1991 ref high cm voltage difference amplifier input cm to op amp is attenuated by resistors r t connected to v term. high negative cm voltage difference amplifier implemented with lt1991. r f = 450k, r g = 450k, r t 50k, gain = 1 v term = v cc = 12v, v ref = 2.5v, v ee = ground. r f m9 m3 m1 p1 p3 p9 v cc v ee r t r t v term v ref input cm range = C60v to 8.3v 12v 2.5v 4pf 4pf table 6. highv cm connections giving difference gains for the lt1991 gain v in + v in C r t noise gain max, min v ext (substitute v cc C 1.2, v ee + 1 for v lim ) 1 p1 m1 2 2 ? v lim - v ref 1 p1 m1 p3, m3 5 5 ? v lim C v ref C 3 ? v term 1 p1 m1 p9, m9 11 11 ? v lim C v ref C 9 ? v term 1 p1 m1 p3||p9 m3||m9 14 14 ? v lim C v ref C 12 ? v term figure 14. extending cm input range applications information lt1991 22 1991ff figure 15. common mode ranges for various lt1991 con? gurations on v s = 3v, 0v; with gain = 1 3v 1991 f15 m9 m3 m1 p1 p3 p9 out v cc v out v in C v in + v in C v in + v in C v in + v in C v in + v ee 3v 3v 3v 3v ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 out v cc v out v ee ref lt1991 8 9 10 1 2 3 7 6 5 4 v cm = 0.8v to 2.35v v cm = 0v to 4v v cm = 2v to 3.6v v dm > 40mv v cm = C1v to 0.6v v dm lt1991 26 1991ff package description 3.00 0.10 (4 sides) note: 1. drawing to be made a jedec package outline m0-229 variation of (weed-2). check the ltc website data sheet for current status of variation assignment 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package 0.38 0.10 bottom view?xposed pad 1.65 0.10 (2 sides) 0.75 0.05 r = 0.115 typ 2.38 0.10 (2 sides) 1 5 10 6 pin 1 top mark (see note 6) 0.200 ref 0.00 ?0.05 (dd10) dfn 1103 0.25 0.05 2.38 0.05 (2 sides) recommended solder pad pitch and dimensions 1.65 0.05 (2 sides) 2.15 0.05 0.50 bsc 0.675 0.05 3.50 0.05 package outline 0.25 0.05 0.50 bsc dd package 10-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1699) lt1991 27 1991ff 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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description msop (ms) 0603 0.53 0.152 (.021 .006) seating plane 0.18 (.007) 1.10 (.043) max 0.17 ?0.27 (.007 ?.011) typ 0.127 0.076 (.005 .003) 0.86 (.034) ref 0.50 (.0197) bsc 12 3 45 4.90 0.152 (.193 .006) 0.497 0.076 (.0196 .003) ref 8 9 10 7 6 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) (note 4) note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 0.254 (.010) 0 ?6 typ detail ? detail ? gauge plane 5.23 (.206) min 3.20 ?3.45 (.126 ?.136) 0.889 0.127 (.035 .005) recommended solder pad layout 0.305 0.038 (.0120 .0015) typ 0.50 (.0197) bsc ms package 10-lead plastic msop (reference ltc dwg # 05-08-1661) lt1991 28 1991ff linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2006 lt 0807 rev f ? printed in usa related parts typical application part number description comments lt1990 high voltage, gain selectable difference ampli? er 250v common mode, micropower, pin selectable gain = 1, 10 lt1991 precision gain selectable difference ampli? er micropower, pin selectable gain = C13 to 14 lt1995 high speed, gain selectable difference ampli? er 30mhz, 1000v/s, pin selectable gain = C7 to 8 lt6010/lt6011/lt6012 single/dual/quad 135a 14nv/ h z rail-to-rail out precision op amp similar op amp performance as used in lt1991 difference ampli? er lt6013/lt6014 single/dual 145a 8nv/ h z rail-to-rail out precision op amp lower noise a v 5 version of lt1991 type op amp ltc6910-x programmable gain ampli? ers 3 gain con? gurations, rail-to-rail input and output v in C v in + v in v cc v s = 2.7v to 36v v s + v s C m9 m3 m1 p1 p3 p9 lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 v ou t lt1991 8 9 10 1 2 3 7 6 5 4 gain = 12 bw = 7hz to 32khz r2* 10k r1 10k v in + C v in C 10k i load = *short r2 for lowest output offset current. include r2 for highest output impedance. 0.1f 1f 1991 ta03 bidirectional current source single supply ac coupled ampli? er v in = 14v to 53v 10 v in 5v 5v m9 m3 m1 p1 p3 p9 v out = lt1991 8 9 10 1 2 3 7 6 5 4 m9 m3 m1 p1 p3 p9 0-4v out lt1991 ref ref 8 9 10 1 2 3 7 6 5 C5v 5v 4 1 4 lt1790 C2.5 v in 13 1f 1991 ta04 2 6 ultra-stable precision attenuator analog level adaptor |
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