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lt1991 1 1991fb , ltc and lt are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. patent pending. precision, 100 a gain selectable amplifier typical applicatio u features descriptio u applicatio s u pin configurable as a difference amplifier, inverting and noninverting amplifier difference amplifier gain range 1 to 13 cmrr >75db noninverting amplifier gain range 0.07 to 14 inverting amplifier gain range C0.08 to C13 gain error <0.04% gain drift < 3ppm/ c wide supply range: single 2.7v to split 18v micropower: 100 a supply current precision: 50 v 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 amplifiers differential to single-ended conversion the lt ? 1991 combines a precision operational amplifier 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 amplifier, where the excellent resistor matching results in a common mode rejection ratio of greater than 75db. the amplifier features a 50 v maximum input offset voltage and a gain bandwidth product of 560khz. the device operates from any supply voltage from 2.7v to 36v and draws only 100 a 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 coefficent is guaranteed less than 3ppm/ c. the resistors are extremely linear with voltage, resulting in a gain nonlinearity of less than 10ppm. the lt1991 is fully specified at 5v and 15v supplies and from C40 c to 85 c. the device is available in space saving 10-lead msop and low profile (0.8mm) 3mm 3mm dfn packages. rail-to-rail gain = 1 difference amplifier distribution of resistor matching 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 C 0.5v to 5.1v r in = 900k ? lt1991 1991 ta01 50k 50k 150k 150k 450k 450k 4pf 450k 450k 4pf resistor matching (%) percentage of units (%) 0.04 1991ta01b C 0.02 0 0.02 40 35 30 25 20 15 10 5 0 C 0.04 450k resistors lt1991a
lt1991 2 1991fb symbol parameter conditions min typ max units ? g gain error v s = 15v, v out = 10v; r l = 10k g = 1; lt1991a 0.04 % g = 1; lt1991 0.08 % g = 3 or 9; lt1991a 0.06 % g = 3 or 9; lt1991 0.12 % gnl gain nonlinearity v s = 15v; v out = 10v; r l = 10k 1 10 ppm ? 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, v s = 15v; v cm = 15.2v referred to inputs (rti) g = 9; lt1991a 80 100 db g = 3; lt1991a 75 93 db g = 1; lt1991a 75 90 db any gain; lt1991 60 70 db v cm input voltage range (note 7) p1/m1 inputs v s = 15v; v ref = 0v C28 27.6 v v s = 5v, 0v; v ref = 2.5v C0.5 5.1 v v s = 3v, 0v; v ref = 1.25v 0.75 2.35 v absolute axi u rati gs w ww u (note 1) electrical characteristics the denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. difference amplifier configuration, v s = 5v, 0v or 15v; v cm = v ref = half supply, unless otherwise noted. total supply voltage (v + to v C ) ............................... 40v input voltage (pins p1/m1, note 2) ....................... 60v input voltage (other inputs note 2).............. v + + 0.2v to v C C 0.2v output short-circuit duration (note 3) ............ indefinite operating temperature range (note 4) ...C40 c to 85 c specified temperature range (note 5) ....C40 c to 85 c order part number dd part marking* t jmax = 150 c, ja = 230 c/w lbmm lt1991cdd lt1991idd LT1991ACDD lt1991aidd *temperature and electrical grades are identified by a label on the shipping container. c onsult ltc marketing for parts specified with wider operating temperature ranges. maximum junction temperature dd package ...................................................... 125 c ms package ..................................................... 150 c storage temperature range dd package .......................................C65 c to 125 c ms package ......................................C65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c order part number ms part marking* ltqd lt1991cms lt1991ims lt1991acms lt1991aims exposed pad connected to v ee pcb connection optional t jmax = 125 c, ja = 160 c/w package/order i for atio uu w 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 1 2 3 4 5 p1 p3 p9 v ee ref 10 9 8 7 6 m1 m3 m9 v cc out top view ms package 10-lead plastic msop
lt1991 3 1991fb symbol parameter conditions min typ max units v cm input voltage range (note 7) p1/m1 inputs, p9/m9 connected to ref v s = 15v; v ref = 0v C60 60 v v s = 5v, 0v; v ref = 2.5v C14 16.8 v v s = 3v, 0v; v ref = 1.25v C1.5 7.3 v p3/m3 inputs v s = 15v; v ref = 0v C15.2 15.2 v v s = 5v, 0v; v ref = 2.5v 0.5 4.2 v v s = 3v, 0v; v ref = 1.25v 0.95 1.95 v p9/m9 inputs v s = 15v; v ref = 0v C15.2 15.2 v v s = 5v, 0v; v ref = 2.5v 0.85 3.9 v v s = 3v, 0v; v ref = 1.25v 1.0 1.9 v v os op amp offset voltage (note 8) lt1991ams, v s = 5v, 0v 15 50 v 135 v lt1991ams, v s = 15v 15 80 v 160 v lt1991ms 25 100 v 200 v lt1991dd 25 150 v 250 v ? v os / ? t op amp offset voltage drift (note 6) 0.3 1 v/ c i b op amp input bias current 2.5 5 na 7.5 na i os op amp input offset current lt1991a 50 500 pa 750 pa lt1991 50 1000 pa 1500 pa op amp input noise voltage 0.01hz to 1hz 0.35 v p-p 0.01hz to 1hz 0.07 v rms 0.1hz to 10hz 0.25 v p-p 0.1hz to 10hz 0.05 v rms e n input noise voltage density g = 1; f = 1khz 180 nv/ hz g = 9; f = 1khz 46 nv/ hz r in input impedance (note 10) p1 (m1 = ground) 630 900 1170 k ? p3 (m3 = ground) 420 600 780 k ? p9 (m9 = ground) 350 500 650 k ? m1 (p1 = ground) 315 450 585 k ? m3 (p3 = ground) 105 150 195 k ? m9 (p9 = ground) 35 50 65 k ? ? r resistor matching 450k resistors, lt1991a 0.01 0.04 % (note 9) other resistors, lt1991a 0.02 0.06 % 450k resistors, lt1991 0.02 0.08 % other resistors, lt1991 0.04 0.12 % ? r/ ? t resistor temperature coefficient (note 6) resistor matching 0.3 3 ppm/ c absolute value C30 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 the denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. difference amplifier configuration, v s = 5v, 0v or 15v; v cm = v ref = half supply, unless otherwise noted. electrical characteristics
lt1991 4 1991fb the denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. difference amplifier configuration, v s = 5v, 0v or 15v; v cm = v ref = half supply, unless otherwise noted. symbol parameter conditions min typ max units v out output voltage swing (to either rail) no load v s = 5v, 0v 40 55 mv v s = 5v, 0v 65 mv v s = 15v 110 mv 1ma load v s = 5v, 0v 150 225 mv v s = 5v, 0v 275 mv v s = 15v 300 mv i sc output short-circuit current (sourcing) drive output positive; 8 12 ma short output to ground 4ma output short-circuit current (sinking) drive output negative; 8 21 ma short output to v s or midsupply 4ma bw C3db bandwidth g = 1 110 khz g = 3 78 khz g = 9 40 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% 3 s g = 9; 0.1v step; 10% to 90% 8 s t s settling time to 0.01% g = 1; v s = 5v, 0v; 2v step 42 s g = 1; v s = 5v, 0v; C2v step 48 s g = 1; v s = 15v, 10v step 114 s g = 1; v s = 15v, C10v step 74 s sr slew rate v s = 5v, 0v; v out = 1v to 4v 0.06 0.12 v/ s v s = 15v; v out = 10v 0.08 0.12 v/ s i s supply current v s = 5v, 0v 100 110 a 150 a v s = 15v 130 160 a 210 a note 1: absolute maximum ratings are those beyond which the life of the device may be impaired. 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 amplifiers). 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 C40 c to 85 c temperature range. note 5: the lt1991c is guaranteed to meet the specified performance from 0 c to 70 c and is designed, characterized and expected to meet specified performance from C40 c to 85 c but is not tested or qa sampled at these temperatures. the lt1991i is guaranteed to meet specified performance from C40 c to 85 c. 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 defined 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 impedence is tested by a combination of direct measurements and correlation to the cmrr and gain error tests. electrical characteristics
lt1991 5 1991fb 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 amplifier configuration) supply current vs supply voltage output voltage swing vs temperature output voltage swing vs load current (output low) typical perfor a ce characteristics uw 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 = 85 c t a = C40 c t a = 25 c 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 1991 g03 2 10 9 8 7 6 5 1 34 v s = 5v, 0v t a = 85 c t a = C40 c t a = 25 c 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 = 85 c t a = C40 c t a = 25 c 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 = 25 c 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)
lt1991 6 1991fb typical perfor a ce characteristics uw output impedance vs frequency cmrr vs temperature gain error vs temperature gain and phase vs frequency gain vs frequency 0.01hz to 1hz voltage noise (difference amplifier configuration) bandwidth vs gain cmrr vs frequency psrr vs frequency 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 = 25 c 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 = 25 c 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 = 25 c gain = 9 gain = 1 gain = 3 frequency (hz) 10 1k 10k 1991 g12 100 100k frequency (hz) output impedance ( ? ) 1 100 1k 100k 10k 1991 g13 10 1000 100 10 1 0.1 0.01 v s = 5v, 0v t a = 25 c 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 10 100 600 1991 g16 gain = 9 gain = 3 gain = 1 v s = 5v, 0v t a = 25 c 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 = 25 c gain = 1 phase gain v s = 15v t a = 25 c measured in g =13 referred to op amp inputs 0 10 2030405060708090100 time (s) op amp voltage noise (100nv/div) 1991 g21
lt1991 7 1991fb block diagra w uu u pi fu ctio s 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 inter- nal 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 amplifier configuration) small signal transient response small signal transient response small signal transient response typical perfor a ce characteristics uw 50mv/div 5 s/div gain = 1 1991 g18 50mv/div 5 s/div 1991 g19 gain = 3 50mv/div 5 s/div gain = 9 1991 g20 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 8 1991fb 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 configure it into several different classical gain circuits without adding external compo- nents. the several pages of simple circuits in this data sheet demonstrate just how easy the lt1991 is to use. it can be configured into difference amplifiers, as well as into inverting and noninverting single ended amplifiers. 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 15 v typical offset voltage and 3na input bias cur- rent. the input offset current is extremely low, so match- ing 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 configurations 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 there- fore 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 configurable gain of 1, the C3db bandwidth is limited to 450khz, with peaking of about 2db at 280khz. in the highest configurable gains, bandwidth is limited to 32khz. input noise the lt1991 input noise is dominated by the johnson noise of the internal resistors ( 4ktr). paralleling all four resistors to the +input gives a 32.1k ? resistance, for 23nv/ hz of voltage noise. the equivalent network on the Cinput gives another 23nv/ hz, and taking their rms sum gives a total 33nv/ hz input referred noise floor. output noise depends on configuration and noise gain. input resistance the lt1991 input resistances vary with configuration, but once configured 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 parallel 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 configuration, 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 applicatio s i for atio wu uu
lt1991 9 1991fb 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 flow 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 configured as a gain of 13 difference amplifier 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 fixed 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 amplifier, with the inputs shorted for the com- mon 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 figure 1. difference amplifier 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 applicatio s i for atio wu u u 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 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, with v more = 0, the op amp output is at v ref . from the max
lt1991 10 1991fb representation of the circuit on the top. the lt1991 is shown on the bottom configured in a precision gain of 5.5. one of the benefits of the noninverting op amp configura- tion is that the input impedance is extremely high. the lt1991 maintains this benefit. given the finite number of available feedback resistors in the lt1991, the number of gain configurations is also finite. the complete list of such hi-z input noninverting gain configurations 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. figure 3. calculating additional voltage range of inverting inputs 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 therefore 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 sug- gested in figure 1: raise v ref , lower v ee , or provide some negative v more . likewise, from the lower common mode extreme, making 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) figure 4. the lt1991 as a classical noninverting op amp applicatio s i for atio wu uu 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 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 amplifier: high input z perhaps the most common op amp configuration is the noninverting amplifier. figure 4 shows the textbook
lt1991 11 1991fb table 1. configuring 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 applicatio s i for atio wu uu
lt1991 12 1991fb figure 5. some implementations of classical noninverting gains using the lt1991. high input z is maintained applicatio s i for atio wu uu 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
lt1991 13 1991fb 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 attenuation using the p input resistors attenuation happens as a matter of fact in difference amplifier configurations, 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 achiev- able 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%. table 2. configuring 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 applicatio s i for atio wu uu 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 count 0 100 10 1 0.1 0.01 150 1991 f07 50 100 200 250 350 300 gain
lt1991 14 1991fb table 3. configuring 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 inverting configuration the inverting amplifier, shown in figure 8, is another classical op amp configuration. the circuit is actually identical to the noninverting amplifier of figure 4, except that v in and gnd have been swapped. the list of available 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 amplifiers. again, for the best dc perfor- mance, match the source impedance seen by the op amp inputs. figure 8. the lt1991 as a classical inverting op amp. note the circuit is identical to the noninverting amplifier, except that v in and ground have been swapped applicatio s i for atio wu uu 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
lt1991 15 1991fb figure 9. it is simple to get precision inverting gains with the lt1991. input impedance varies from 45k ? (gain = C13) to 450k ? (gain = C1) applicatio s i for atio wu uu 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
lt1991 16 1991fb figure 10. difference amplifier 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 difference amplifiers the resistors in the lt1991 allow it to easily make differ- ence amplifiers also. figure 10 shows the basic 4-resistor difference amplifier 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 parallel, 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 amplifiers, the noise gain is 1 more than the signal gain. 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 applicatio s i for atio wu uu 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 f10 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
lt1991 17 1991fb figure 11. many difference gains are achievable just by strapping the pins applicatio s i for atio wu uu 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
lt1991 18 1991fb 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 figure 13. integer gain difference amplifiers using cross-coupling difference amplifier: additional integer gains using cross-coupling figure 12 shows the basic difference amplifier 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 differ- ential 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 inspec- tion from the v in + connections, and that the v in C connec- tions are simply the opposite (swap p for m and m for p). noise gain, bandwidth, and input impedance specifica- tions for the various cases are also tabulated, as these are not obvious. schematics are provided in figure 13. table 5. connections using cross-coupling. note that equations can be written by inspection of the v in + column noise C3db bw r in + r in C gain v in + v in C equation gain khz typ k ? 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. applicatio s i for atio wu uu 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 f10 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 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
lt1991 19 1991fb high voltage cm difference amplifiers this class of difference amplifier 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, because 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 equation has been simplified and evaluated, and the re- sulting equations provided in table 6. as before, substi- tuting 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 negative common mode limit. several more examples of high cm circuits are shown in figures 15, 16, 17 for various supplies. figure 14. extending cm input range table 6. highv cm connections giving difference gains for the lt1991 max, min v ext noise (substitute v cc C 1.2, gain v in + v in C r t gain 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 14 14 ? v lim C v ref C 12 ? v term m3||m9 applicatio s i for atio wu uu 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
lt1991 20 1991fb applicatio s i for atio wu uu 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 21 1991fb applicatio s i for atio wu uu 4 3v 1991 f16 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 5v 5v 5v 5v 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 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 = C0.5v to 5.1v v cm = C5v to 9v v cm = 2v to 7.6v v dm > 40mv v cm = C3v to 2.6v v dm lt1991 22 1991fb figure 17. common mode ranges for various lt1991 configurations on v s = 5v, with gain = 1 applicatio s i for atio wu uu 1991 f17 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 5v 5v 5v 5v 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 = C8v to 7.6v v cm = C20v to 19v v cm = C3v to 12.6v v dm > 40mv v cm = C13v to 2.6v v dm lt1991 23 1991fb ms package 10-lead plastic msop (reference ltc dwg # 05-08-1661) u package descriptio 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 its circuits as described herein will not infringe on existing patent rights. msop (ms) 0603 0.53 0.152 (.021 .006) seating plane 0.18 (.007) 1.10 (.043) max 0.17 C 0.27 (.007 C .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 C 6 typ detail a detail a gauge plane 5.23 (.206) min 3.20 C 3.45 (.126 C .136) 0.889 0.127 (.035 .005) recommended solder pad layout 0.305 0.038 (.0120 .0015) typ 0.50 (.0197) bsc
lt1991 24 1991fb linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2004 lt/tp 0105 1k rev b ? printed in usa typical applicatio u related parts part number description comments lt1990 high voltage, gain selectable difference amplifier 250v common mode, micropower, pin selectable gain = 1, 10 lt1991 precision gain selectable difference amplifier micropower, pin selectable gain = C13 to 14 lt1995 high speed, gain selectable difference amplifier 30mhz, 1000v/ s, pin selectable gain = C7 to 8 lt6010/lt6011/lt6012 single/dual/quad 135 a 14nv/ hz rail-to-rail out similar op amp performance as precision op amp used in lt1991 difference amplifier lt6013/lt6014 single/dual 145 a 8nv/ hz rail-to-rail out lower noise a v 5 version of lt1991 type op amp precision op amp ltc6910-x programmable gain amplifiers 3 gain configurations, rail-to-rail input and output micropower a v = 10 instrumentation amplifier bidirectional current source single supply ac coupled amplifier C + C + v m v p v out lt1991 1991 ta02 98 23 4 5 7 6 10 1 C + 1/2 lt6011 1/2 lt6011 4pf 4pf 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 out 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. 0.1 f 1 f 1991 ta03

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