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1 LT1920 single resistor gain programmable, precision instrumentation amplifier the lt ? 1920 is a low power, precision instrumentation amplifier that requires only one external resistor to set gains of 1 to 10,000. the low voltage noise of 7.5nv/ ? hz (at 1khz) is not compromised by low power dissipation (0.9ma typical for 2.3v to 15v supplies). the high accuracy of 30ppm maximum nonlinearity and 0.3% max gain error (g = 10) is not degraded even for load resistors as low as 2k (previous monolithic instrumentation amps used 10k for their nonlinearity specifications). the LT1920 is laser trimmed for very low input offset voltage (125 m v max), drift (1 m v/ c), high cmrr (75db, g = 1) and psrr (80db, g = 1). low input bias currents of 2na max are achieved with the use of superbeta processing. the output can handle capacitive loads up to 1000pf in any gain configu- ration while the inputs are esd protected up to 13kv (human body). the LT1920 with two external 5k resistors passes the iec 1000-4-2 level 4 specification. the LT1920, offered in 8-pin pdip and so packages, is a pin for pin and spec for spec improved replacement for the ad620. the LT1920 is the most cost effective solution for precision instrumentation amplifier applications. for even better guaranteed performance, see the lt1167. n single gain set resistor: g = 1 to 10,000 n gain error: g = 10, 0.3% max n gain nonlinearity: g = 10, 30ppm max n input offset voltage: g = 10, 225 m v max n input offset voltage drift: 1 m v/ c max n input bias current: 2na max n psrr at g = 1: 80db min n cmrr at g = 1: 75db min n supply current: 1.3ma max n wide supply range: 2.3v to 18v n 1khz voltage noise: 7.5nv/ ? hz n 0.1hz to 10hz noise: 0.28 m v p-p n available in 8-pin pdip and so packages n meets iec 1000-4-2 level 4 esd tests with two external 5k resistors , ltc and lt are registered trademarks of linear technology corporation. n bridge amplifiers n strain gauge amplifiers n thermocouple amplifiers n differential to single-ended converters n medical instrumentation nonlinearity (100ppm/div) output voltage (2v/div) g = 1000 r l = 1k v out = 10v 1167 ta02 gain nonlinearity single supply barometer + + + 2 1 1 1 1 2 r5 392k r4 50k r3 50k r8 100k r6 1k lt1634ccz-1.25 8 4 1/2 lt1490 3 r set v s = 8v to 30v 5k 5k 5k 5k v s 5 4 3 2 + 7 1/2 lt1490 5 6 2 8 lucas nova senor npc-1220-015-a-3l 7 v s 6 1920 ta01 5 to 4-digit dvm 4 r2 12 LT1920 g = 60 r1 825 3 6 r7 50k volts 2.800 3.000 3.200 inches hg 28.00 30.00 32.00 features descriptio u applicatio s u typical applicatio u
2 LT1920 absolute m axi m u m ratings w ww u order part number package/order i n for m atio n w u u LT1920cn8 LT1920cs8 LT1920in8 LT1920is8 s8 part marking 1920 1920i 1 2 3 4 8 7 6 5 top view r g in +in ? s r g +v s output ref n8 package 8-lead pdip s8 package 8-lead plastic so + t jmax = 150 c, q ja = 130 c/ w (n8) t jmax = 150 c, q ja = 190 c/ w (s8) (note 1) supply voltage ...................................................... 20v differential input voltage (within the supply voltage) ..................................................... 40v input voltage (equal to supply voltage) ................ 20v input current (note 3) ........................................ 20ma output short-circuit duration .......................... indefinite operating temperature range ................ C 40 c to 85 c specified temperature range LT1920c (note 4) .................................... 0 c to 70 c LT1920i .............................................. C 40 c to 85 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c consult factory for military grade parts. electrical characteristics v s = 15v, v cm = 0v, t a = 25 c, r l = 2k, unless otherwise noted. symbol parameter conditions (note 6) min typ max units g gain range g = 1 + (49.4k/r g ) 1 10k gain error g = 1 0.008 0.1 % g = 10 (note 2) 0.010 0.3 % g = 100 (note 2) 0.025 0.3 % g = 1000 (note 2) 0.040 0.35 % g/t gain vs temperature g < 1000 (note 2) l 20 50 ppm/ c gain nonlinearity (note 5) v o = 10v, g = 1 10 ppm v o = 10v, g = 10 and 100 10 30 ppm v o = 10v, g = 100 and 1000 20 ppm v ost total input referred offset voltage v ost = v osi + v oso /g v osi input offset voltage g = 1000, v s = 5v to 15v 30 125 m v g = 1000, v s = 5v to 15v l 185 m v v osi /t input offset drift (rti) (note 3) l 1 m v/ c v oso output offset voltage g = 1, v s = 5v to 15v 400 1000 m v g = 1, v s = 5v to 15v l 1500 m v v oso /t output offset drift (note 3) l 515 m v/ c i os input offset current 0.3 1 na i b input bias current 0.5 2 na e n input noise voltage, rti 0.1hz to 10hz, g = 1 2.00 m v p-p 0.1hz to 10hz, g = 10 0.50 m v p-p 0.1hz to 10hz, g = 100 and 1000 0.28 m v p-p total rti noise = ? e ni 2 + (e no /g) 2 e ni input noise voltage density, rti f o = 1khz 7.5 nv/ ? hz e no output noise voltage density, rti f o = 1khz 67 nv/ ? hz i n input noise current f o = 0.1hz to 10hz 10 pa p-p input noise current density f o = 10hz 124 fa/ ? hz r in input resistance v in = 10v 200 g w c in(diff) differential input capacitance f o = 100khz 1.6 pf
3 LT1920 electrical characteristics v s = 15v, v cm = 0v, t a = 25 c, r l = 2k, unless otherwise noted. symbol parameter conditions (note 6) min typ max units c in(cm) common mode input capacitance f o = 100khz 1.6 pf v cm input voltage range g = 1, other input grounded v s = 2.3v to 5v Cv s + 1.9 +v s C 1.2 v v s = 5v to 18v Cv s + 1.9 +v s C 1.4 v v s = 2.3v to 5v l Cv s + 2.1 +v s C 1.3 v v s = 5v to 18v l Cv s + 2.1 +v s C 1.4 v cmrr common mode rejection ratio 1k source imbalance, v cm = 0v to 10v g = 1 75 95 db g = 10 95 115 db g = 100 110 125 db g = 1000 110 140 db psrr power supply rejection ratio v s = 2.3 to 18v g = 1 80 120 db g = 10 100 135 db g = 100 120 140 db g = 1000 120 150 db i s supply current v s = 2.3v to 18v 0.9 1.3 ma v out output voltage swing r l = 10k v s = 2.3v to 5v Cv s + 1.1 +v s C 1.2 v v s = 5v to 18v Cv s + 1.2 +v s C 1.3 v v s = 2.3v to 5v l Cv s + 1.4 +v s C 1.3 v v s = 5v to 18v l Cv s + 1.6 +v s C 1.5 v i out output current 20 27 ma bw bandwidth g = 1 1000 khz g = 10 800 khz g = 100 120 khz g = 1000 12 khz sr slew rate g = 1, v out = 10v 1.2 v/ m s settling time to 0.01% 10v step g = 1 to 100 14 m s g = 1000 130 m s r refin reference input resistance 20 k w i refin reference input current v ref = 0v 50 m a v ref reference voltage range C v s + 1.6 +v s C 1.6 v a vref reference gain to output 1 0.0001 the l denotes specifications that apply over the full specified temperature range. note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: does not include the effect of the external gain resistor r g . note 3: this parameter is not 100% tested. note 4: the LT1920c is designed, characterized and expected to meet the industrial temperature limits, but is not tested at C 40 c and 85 c. i-grade parts are guaranteed. note 5: this parameter is measured in a high speed automatic tester that does not measure the thermal effects with longer time constants. the magnitude of these thermal effects are dependent on the package used, heat sinking and air flow conditions. note 6: typical parameters are defined as the 60% of the yield parameter distribution.
4 LT1920 typical perfor a ce characteristics uw gain nonlinearity, g = 1 nonlinearity (1ppm/div) output voltage (2v/div) g = 1 r l = 2k v out = 10v 1167 g01 gain nonlinearity, g = 10 nonlinearity (10ppm/div) output voltage (2v/div) 1167 g02 g = 10 r l = 2k v out = 10v gain nonlinearity, g = 100 nonlinearity (10ppm/div) output voltage (2v/div) g = 100 r l = 2k v out = 10v 1167 g03 gain nonlinearity, g = 1000 nonlinearity (100ppm/div) output voltage (2v/div) g = 1000 r l = 2k v out = 10v 1167 g04 warm-up drift time after power on (minutes) 0 10 12 s8 n8 14 34 1920 g09 8 6 12 5 4 2 0 change in offset voltage ( m v) v s = 15v t a = 25 c g = 1 gain error vs temperature temperature ( c) ?0 gain error (%) 0.20 0.10 0.05 0 50 0.20 1920 g06 0.15 0 ?5 75 g = 1 25 100 0.05 0.10 0.15 v s = 15v v out = 10v r l = 2k *does not include temperature effects of r g g = 10* g = 1000* g = 100* frequency (hz) 0.1 common mode rejection ratio (db) 60 80 100 100 10k 1920 g14 40 20 0 110 1k 120 140 160 100k g = 1000 g = 100 g = 10 g = 1 v s = 15v t a = 25 c 1k source imbalance common mode rejection ratio vs frequency frequency (hz) 0.1 negative power supply rejection ratio (db) 60 80 100 100 10k 1920 g15 40 20 0 110 1k 120 140 160 100k g = 1000 g = 100 g = 10 g = 1 v + = 15v t a = 25 c negative power supply rejection ratio vs frequency common mode input voltage (v) ?5 input bias current (pa) 100 300 500 9 1920 g13 ?00 300 0 200 400 200 400 500 ? ? 3 ?2 12 ? 0 6 15 ?0 c 85 c 0 c 70 c 25 c input bias current vs common mode input voltage
5 LT1920 typical perfor a ce characteristics uw frequency (hz) 0.1 positive power supply rejection ratio (db) 60 80 100 100 10k 1920 g16 40 20 0 110 1k 120 140 160 100k g = 1000 g = 10 g = 1 v = 15v t a = 25 c g = 100 positive power supply rejection ratio vs frequency gain vs frequency frequency (khz) 0 gain (db) 10 30 50 60 0.01 1 10 1000 1920 g17 ?0 0.1 100 40 20 ?0 g = 1000 g = 100 g = 10 g = 1 v s = 15v t a = 25 c supply current vs supply voltage supply voltage ( v) 0 supply current (ma) 1.00 1.25 85 c 25 c ?0 c 20 1920 g18 0.75 0.50 5 10 15 1.50 0.1hz to 10hz noise voltage, rti g = 1000 time (sec) 0 noise voltage (0.2 m v/div) 8 1920 g21 2 4 5 10 6 1 3 9 7 v s = 15v t a = 25 c frequency (hz) 1 0 100 1000 10 100 1k 100k 10k 1920 g19 10 voltage noise density (nv ? hz) v s = 15v t a = 25 c 1/f corner = 10hz 1/f corner = 9hz 1/f corner = 7hz gain = 1 gain = 10 gain = 100, 1000 bw limit gain = 1000 voltage noise density vs frequency time (sec) 0 noise voltage (2 m v/div) 8 1920 g20 2 4 5 10 6 1 3 9 7 v s = 15v t a = 25 c 0.1hz to 10hz noise voltage, g = 1 current noise density vs frequency frequency (hz) 1 10 current noise density (fa/ ? hz) 100 1000 10 100 1000 1920 g22 v s = 15v t a = 25 c r s time from output short to ground (minutes) 0 ?0 (sink) (source) output current (ma) ?0 ?0 ?0 0 50 20 1 2 1920 g24 ?0 30 40 10 3 t a = 40 c v s = 15v t a = 40 c t a = 25 c t a = 85 c t a = 85 c t a = 25 c short-circuit current vs time time (sec) 0 current noise (5pa/div) 8 1920 g23 2 4 5 10 6 1 3 9 7 v s = 15v t a = 25 c 0.1hz to 10hz current noise
6 LT1920 typical perfor a ce characteristics uw overshoot vs capacitive load capacitive load (pf) 10 40 overshoot (%) 50 60 70 80 100 1000 10000 1920 g25 30 20 10 0 90 100 v s = 15v v out = 50mv r l = a v 3 100 a v = 10 a v = 1 undistorted output swing vs frequency frequency (khz) 1 20 25 peak-to-peak output swing (v) 30 35 10 100 1000 1920 g27 15 10 5 0 g = 1 g = 10, 100, 1000 v s = 15v t a = 25 c output impedance vs frequency frequency (khz) 1 output impedance ( w ) 10 100 1000 10 100 1000 1920 g26 0.1 1 v s = 15v t a = 25 c g = 1 to 1000 5v/div 10 m s/div large-signal transient response 1167 g28 g = 1 v s = 15v r l = 2k c l = 60pf 5v/div 10 m s/div large-signal transient response g = 10 v s = 15v r l = 2k c l = 60pf 1167 g31 5v/div 10 m s/div large-signal transient response 1167 g34 g = 100 v s = 15v r l = 2k c l = 60pf 20mv/div 10 m s/div g = 10 v s = 15v r l = 2k c l = 60pf small-signal transient response 1167 g32 20mv/div 10 m s/div g = 1 v s = 15v r l = 2k c l = 60pf small-signal transient response 1167 g29 20mv/div 10 m s/div g = 100 v s = 15v r l = 2k c l = 60pf small-signal transient response 1167 g35
7 LT1920 typical perfor a ce characteristics uw 50 m s/div large-signal transient response g = 1000 v s = 15v r l = 2k c l = 60pf 5v/div 1167 g37 gain (db) 1 1 settling time ( m s) 10 100 1000 10 100 1000 1920 g30 v s = 15v t a = 25 c d v out = 10v 1mv = 0.01% settling time vs gain 50 m s/div small-signal transient response g = 1000 v s = 15v r l = 2k c l = 60pf 20mv/div 1167 g38 slew rate vs temperature temperature ( c) ?0 25 0.8 slew rate (v/ m s) 1.2 1.8 0 50 75 1920 g36 1.0 1.6 1.4 25 100 125 v s = 15v v out = 10v g = 1 + slew slew settling time vs step size settling time ( m s) 2 output step (v) 2 6 10 10 1920 g33 ? ? 0 4 8 ? ? ?0 4 6 8 311 5 7 9 12 0v v out to 0.1% to 0.1% to 0.01% to 0.01% 0v v out v s = 15 g = 1 t a = 25 c c l = 30pf r l = 1k output voltage swing vs load current output current (ma) output voltage swing (v) (referred to supply voltage) +v s +v s ?0.5 +v s ?1.0 +v s ?1.5 +v s ?2.0 ? s + 2.0 ? s + 1.5 ? s + 1.0 ? s + 0.5 ? s 0.01 1 10 100 1920 g39 0.1 v s = 15v 85 c 25 c ?0 c source sink
8 LT1920 with programmed gain. therefore, the bandwidth does not drop proportional to gain. the input transistors q1 and q2 offer excellent matching, which is inherent in npn bipolar transistors, as well as picoampere input bias current due to superbeta process- ing. the collector currents in q1 and q2 are held constant due to the feedback through the q1-a1-r1 loop and q2-a2-r2 loop which in turn impresses the differential input voltage across the external gain set resistor r g . since the current that flows through r g also flows through r 1 and r2, the ratios provide a gained-up differential volt- age, g = (r1 + r2)/r g , to the unity-gain difference amplifier a3. the common mode voltage is removed by a3, result- ing in a single-ended output voltage referenced to the voltage on the ref pin. the resulting gain equation is: v out C v ref = g(v in + C v in C ) where: g = (49.4k w /r g ) + 1 solving for the gain set resistor gives: r g = 49.4k w /(g C 1) theory of operatio u the LT1920 is a modified version of the three op amp instrumentation amplifier. laser trimming and monolithic construction allow tight matching and tracking of circuit parameters over the specified temperature range. refer to the block diagram (figure 1) to understand the following circuit description. the collector currents in q1 and q2 are trimmed to minimize offset voltage drift, thus assuring a high level of performance. r1 and r2 are trimmed to an absolute value of 24.7k to assure that the gain can be set accurately (0.3% at g = 100) with only one external resistor r g . the value of r g in parallel with r1 (r2) determines the transconductance of the preamp stage. as r g is reduced for larger programmed gains, the transcon- ductance of the input preamp stage increases to that of the input transistors q1 and q2. this increases the open-loop gain when the programmed gain is increased, reducing the input referred gain related errors and noise. the input voltage noise at gains greater than 50 is determined only by q1 and q2. at lower gains the noise of the difference amplifier and preamp gain setting resistors increase the noise. the gain bandwidth product is determined by c1, c2 and the preamp transconductance which increases block diagra m w q1 r g 2 output 6 ref 1920 f01 5 7 + a1 + a3 vb r1 24.7k r3 400 w r4 400 w c1 1 r g 8 r7 10k r8 10k r5 10k r6 10k difference amplifier stage preamp stage +in ?n 3 + a2 vb r2 24.7k c2 v + v v v + v q2 v v + 4 v figure 1. block diagram
9 LT1920 input and output offset voltage the offset voltage of the LT1920 has two components: the output offset and the input offset. the total offset voltage referred to the input (rti) is found by dividing the output offset by the programmed gain (g) and adding it to the input offset. at high gains the input offset voltage domi- nates, whereas at low gains the output offset voltage dominates. the total offset voltage is: total input offset voltage (rti) = input offset + (output offset/g) total output offset voltage (rto) = (input offset ? g) + output offset reference terminal the reference terminal is one end of one of the four 10k resistors around the difference amplifier. the output volt- age of the LT1920 (pin 6) is referenced to the voltage on the reference terminal (pin 5). resistance in series with the ref pin must be minimized for best common mode rejection. for example, a 2 w resistance from the ref pin to ground will not only increase the gain error by 0.02% but will lower the cmrr to 80db. single supply operation for single supply operation, the ref pin can be at the same potential as the negative supply (pin 4) provided the output of the instrumentation amplifier remains inside the specified operating range and that one of the inputs is at least 2.5v above ground. the barometer application on the front page of this data sheet is an example that satisfies these conditions. the resistance r set from the bridge transducer to ground sets the operating current for the bridge and also has the effect of raising the input common mode voltage. the output of the LT1920 is always inside the specified range since the barometric pressure rarely goes low enough to cause the output to rail (30.00 inches of hg corresponds to 3.000v). for applications that re- quire the output to swing at or below the ref potential, the voltage on the ref pin can be level shifted. an op amp is used to buffer the voltage on the ref pin since a parasitic series resistance will degrade the cmrr. the application in the back of this data sheet, four digit pressure sensor, is an example. theory of operatio u output offset trimming the LT1920 is laser trimmed for low offset voltage so that no external offset trimming is required for most applica- tions. in the event that the offset needs to be adjusted, the circuit in figure 2 is an example of an optional offset adjust circuit. the op amp buffer provides a low impedance to the ref pin where resistance must be kept to minimum for best cmrr and lowest gain error. input bias current return path the low input bias current of the LT1920 (2na) and the high input impedance (200g w ) allow the use of high impedance sources without introducing additional offset voltage errors, even when the full common mode range is required. however, a path must be provided for the input bias currents of both inputs when a purely differential signal is being amplified. without this path the inputs will float to either rail and exceed the input common mode range of the LT1920, resulting in a saturated input stage. figure 3 shows three examples of an input bias current path. the first example is of a purely differential signal source with a 10k w input current path to ground. since the impedance of the signal source is low, only one resistor is needed. two matching resistors are needed for higher impedance signal sources as shown in the second example. balancing the input impedance improves both common mode rejection and dc offset. the need for input resistors is eliminated if a center tap is present as shown in the third example. + 2 ?n output +in 1 8 10k 100 100 ?0mv 1920 f02 v v + 10mv 5 2 3 1 6 1/2 lt1112 10mv adjustment range r g 3 + LT1920 ref figure 2. optional trimming of output offset voltage
10 LT1920 theory of operatio u figure 3. providing an input common mode current path applicatio n s i n for m atio n wu u u 10k r g r g r g 1920 f03 thermocouple 200k microphone, hydrophone, etc 200k center-tap provides bias current return + LT1920 + LT1920 + LT1920 the LT1920 is a low power precision instrumentation amplifier that requires only one external resistor to accu- rately set the gain anywhere from 1 to 1000. the output can handle capacitive loads up to 1000pf in any gain configuration and the inputs are protected against esd strikes up to 13kv (human body). input protection the LT1920 can safely handle up to 20ma of input current in an overload condition. adding an external 5k input resistor in series with each input allows dc input fault voltages up to 100v and improves the esd immu- nity to 8kv (contact) and 15kv (air discharge), which is the iec 1000-4-2 level 4 specification. if lower value input resistors are needed, a clamp diode from the positive supply to each input will maintain the iec 1000-4-2 specification to level 4 for both air and contact discharge. a 2n4393 drain/source to gate is a good low leakage diode for use with 1k resistors, see figure 4. the input resistors should be carbon and not metal film or carbon film. rfi reduction in many industrial and data acquisition applications, instrumentation amplifiers are used to accurately amplify small signals in the presence of large common mode voltages or high levels of noise. typically, the sources of these very small signals (on the order of microvolts or millivolts) are sensors that can be a significant distance from the signal conditioning circuit. although these sen- figure 4. input protection v ee 1920 f04 v cc v cc v cc j2 2n4393 j1 2n4393 out optional for highest esd protection r g r in r in + LT1920 ref sors may be connected to signal conditioning circuitry, using shielded or unshielded twisted-pair cabling, the ca- bling may act as antennae, conveying very high frequency interference directly into the input stage of the LT1920. the amplitude and frequency of the interference can have an adverse effect on an instrumentation amplifiers input stage by causing an unwanted dc shift in the amplifiers input offset voltage. this well known effect is called rfi rectification and is produced when out-of-band interfer- ence is coupled (inductively, capacitively or via radiation) and rectified by the instrumentation amplifiers input tran- sistors. these transistors act as high frequency signal detectors, in the same way diodes were used as rf envelope detectors in early radio designs. regardless of the type of interference or the method by which it is coupled into the circuit, an out-of-band error signal ap- pears in series with the instrumentation amplifiers inputs.
11 LT1920 applicatio n s i n for m atio n wu u u to significantly reduce the effect of these out-of-band signals on the input offset voltage of instrumentation amplifiers, simple lowpass filters can be used at the inputs. this filter should be located very close to the input pins of the circuit. an effective filter configuration is illustrated in figure 5, where three capacitors have been added to the inputs of the LT1920. capacitors c xcm1 and c xcm2 form lowpass filters with the external series resis- tors r s1, 2 to any out-of-band signal appearing on each of the input traces. capacitor c xd forms a filter to reduce any unwanted signal that would appear across the input traces. an added benefit to using c xd is that the circuits ac common mode rejection is not degraded due to common mode capacitive imbalance. the differential mode and common mode time constants associated with the capaci- tors are: t dm(lpf) = (2)(r s )(c xd ) t cm(lpf) = (r s1, 2 )(c xcm1, 2 ) setting the time constants requires a knowledge of the frequency, or frequencies of the interference. once this frequency is known, the common mode time constants can be set followed by the differential mode time constant. set the common mode time constants such that they do not degrade the LT1920s inherent ac cmr. then the differential mode time constant can be set for the band- width required for the application. setting the differential mode time constant close to the sensors bw also mini- mizes any noise pickup along the leads. to avoid any possibility of inadvertently affecting the signal to be pro- cessed, set the common mode time constant an order of magnitude (or more) larger than the differential mode time constant. to avoid any possibility of common mode to differential mode signal conversion, match the common mode time constants to 1% or better. if the sensor is an rtd or a resistive strain gauge, then the series resistors r s1, 2 can be omitted, if the sensor is in proximity to the instrumentation amplifier. n8 1197 0.100 0.010 (2.540 0.254) 0.065 (1.651) typ 0.045 ?0.065 (1.143 ?1.651) 0.130 0.005 (3.302 0.127) 0.020 (0.508) min 0.018 0.003 (0.457 0.076) 0.125 (3.175) min 12 3 4 87 6 5 0.255 0.015* (6.477 0.381) 0.400* (10.160) max 0.009 ?0.015 (0.229 ?0.381) 0.300 ?0.325 (7.620 ?8.255) 0.325 +0.035 0.015 +0.889 0.381 8.255 () *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.010 inch (0.254mm) n8 package 8-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) dimensions in inches (millimeters) unless otherwise noted. package descriptio n u figure 5. adding a simple rc filter at the inputs to an instrumentation amplifier is effective in reducing rectification of high frequency out-of-band signals 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. v v + in + in 1920 f05 v out r g c xcm1 0.001 f c xcm2 0.001 f c xd 0.1 f r s1 1.6k r s2 1.6k external rfi filter + LT1920 f(?db) 500hz
12 LT1920 1920f lt/tp 0299 4k ? printed in usa ? linear technology corpora tion 1998 typical applicatio n u linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear-tech.com part number description comments ltc1100 precision chopper-stabilized instrumentation amplifier best dc accuracy lt1101 precision, micropower, single supply instrumentation amplifier fixed gain of 10 or 100, i s < 105 m a lt1102 high speed, jfet instrumentation amplifier fixed gain of 10 or 100, 30v/ m s slew rate lt1167 single resistor gain programmable precision upgraded version of the LT1920 instrumentation amplifier ltc ? 1418 14-bit, low power, 200ksps adc with serial and parallel i/o single supply 5v or 5v operation, 1.5lsb inl and 1lsb dnl max lt1460 precision series reference micropower; 2.5v, 5v, 10v versions; high precision ltc1562 active rc filter lowpass, bandpass, highpass responses; low noise, low distortion, four 2nd order filter sections ltc1605 16-bit, 100ksps, sampling adc single 5v supply, bipolar input range: 10v, power dissipation: 55mw typ related parts package descriptio n u dimensions in inches (millimeters) unless otherwise noted. nerve impulse amplifier 2 2 ?n patient ground output 1v/mv +in 1 1 8 r6 1m r7 10k r8 100 1920 ta03 a v = 101 pole at 1khz 5 5 4 ?v ?v 3v 3v 7 6 8 4 7 6 + 1/2 lt1112 1/2 lt1112 r4 30k r3 30k r1 12k c1 0.01 m f r g 6k 3 3 r2 1m c2 0.47 f 0.3hz highpass c3 15nf patient/circuit protection/isolation + LT1920 g = 10 + s8 package 8-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) 1 2 3 4 0.150 ?0.157** (3.810 ?3.988) 8 7 6 5 0.189 ?0.197* (4.801 ?5.004) 0.228 ?0.244 (5.791 ?6.197) 0.016 ?0.050 0.406 ?1.270 0.010 ?0.020 (0.254 ?0.508) 45 0 ?8 typ 0.008 ?0.010 (0.203 ?0.254) so8 0996 0.053 ?0.069 (1.346 ?1.752) 0.014 ?0.019 (0.355 ?0.483) 0.004 ?0.010 (0.101 ?0.254) 0.050 (1.270) typ dimension does not include mold flash. mold flash shall not exceed 0.006" (0.152mm) per side dimension does not include interlead flash. interlead flash shall not exceed 0.010" (0.254mm) per side * **

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