® INA131 INA131 Precision G = 100 INSTRUMENTATION AMPLIFIER FEATURES DESCRIPTION l LOW OFFSET VOLTAGE: 50m V max The INA131 is a low cost, general purpose G = 100 l LOW DRIFT: 0.25m V/(cid:176) C max instrumentation amplifier offering excellent accuracy. Its 3-op amp design and small size make it ideal for l LOW INPUT BIAS CURRENT: 2nA max a wide range of applications. l HIGH COMMON-MODE REJECTION: On-chip laser trimmed resistors accurately set a fixed 110dB min gain of 100. The INA131 is laser trimmed to achieve l INPUT OVERVOLTAGE PROTECTION: very low offset voltage (50m V max), drift (0.25m V/(cid:176) C – 40V max), and high CMR (110dB min). Internal input l WIDE SUPPLY RANGE: – 2.25 to – 18V protection can withstand up to – 40V inputs without l LOW QUIESCENT CURRENT: 3mA damage. l 8-PIN PLASTIC DIP The INA131 is available in a 8-pin plastic DIP. They are specified over the –40(cid:176) C to +85(cid:176) C temperature range. APPLICATIONS l BRIDGE AMPLIFIER l THERMOCOUPLE AMPLIFIER l RTD SENSOR AMPLIFIER l MEDICAL INSTRUMENTATION l DATA ACQUISITION V+ 7 – 2 Over-Voltage INA131 V IN Protection A 1 5kW 25kW 1 25kW 6 + – 2.63kW A3 VO = 100 (VIN – VIN) 8 25kW 5 A Ref V+ 3 Over-Voltage 2 5kW 25kW IN Protection 4 DIP V– International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111 Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 ©1992 Burr-Brown Corporation PDS-1144E Printed in U.S.A. March, 1998 SBOS016

SPECIFICATIONS At T = +25(cid:176)C, V = – 15V, R = 2kW , unless otherwise noted. A S L INA131BP INA131AP PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS INPUT Offset Voltage, RTI Initial T = +25(cid:176)C – 10 – 50 – 25 – 125 m V A vs Temperature T = T to T – 0.1 – 0.25 – 0.25 – 1 m V/(cid:176)C A MIN MAX vs Power Supply V = – 2.25V to – 18V 0.5 3 [ [ m V/V S Long-Term Stability 0.2 [ m V/mo Impedance, Differential 1010 || 6 [ W || pF Common-Mode 1010 || 6 [ W || pF Input Common-Mode Range – 11 – 13.5 [ [ V Safe Input Voltage – 40 [ V Common-Mode Rejection V = – 10V, D R = 1kW 110 120 106 110 dB CM S BIAS CURRENT – 0.5 – 2 [ – 5 nA vs Temperature – 8 [ pA/(cid:176)C OFFSET CURRENT – 0.5 – 2 [ – 5 nA vs Temperature – 8 [ pA/(cid:176)C NOISE VOLTAGE, RTI R = 0W S f = 10Hz 16 [ nV/(cid:214) Hz f = 100Hz 12 [ nV/(cid:214) Hz f = 1kHz 12 [ nV/(cid:214) Hz f = 10kHz 12 [ nV/(cid:214) Hz f = 0.1Hz to 10Hz 0.4 [ m Vp-p B Noise Current f = 10Hz 0.4 [ pA/(cid:214) Hz f= 1kHz 0.2 [ pA/(cid:214) Hz f = 0.1Hz to 100Hz 18 [ pAp-p B GAIN Gain Error(1) – 0.01 – 0.024 [ – 0.1 % Resistor Value(2) – 10 – 40 [ [ % Gain vs Temperature – 5 – 10 [ – 20 ppm/(cid:176)C Nonlinearity – 0.0003 – 0.002 [ – 0.004 % of FSR OUTPUT Voltage I = 5mA, T to T – 13.5 – 13.7 [ [ V O MIN MAX V = – 11.4V, R = 2kW – 10 10.5 [ [ V S L V = – 2.25V, R = 2kW – 1 1.5 [ [ V S L Load Capacitance, max Stable Operation 1000 [ pF Short Circuit Current +20/–15 [ mA FREQUENCY RESPONSE Bandwidth, –3dB 70 [ kHz Slew Rate V = – 10V 0.3 0.7 [ [ V/m s O Settling Time, 0.01% 100 [ m s Overload Recovery 50% Overdrive 20 [ m s POWER SUPPLY Voltage Range – 2.25 – 15 – 18 [ [ [ V Current V = 0V – 2.2 – 3 [ [ mA IN TEMPERATURE RANGE Specification –40 85 [ [ (cid:176)C Operating –40 125 [ [ (cid:176)C q 100 [ (cid:176)C/W JA [ Specification same as INA131BP. NOTES: (1) R = 10kW . (2) Absolute value of internal gain-setting resistors. (Gain depends on resistor ratios.) L The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems. ® INA131 2

PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS(1) Top View P-Package/8-Pin DIP Supply Voltage..................................................................................– 18V Input Voltage Range..........................................................................– 40V Output Short Circuit (to ground)..............................................Continuous RG 1 8 RG Operating Temperature..................................................–40(cid:176)C to +125(cid:176)C V– 2 7 V+ Storage Temperature.....................................................–40(cid:176)C to +125(cid:176)C IN Junction Temperature....................................................................+150(cid:176)C V+ 3 6 V Lead Temperature (soldering –10s)..............................................+300(cid:176)C IN O NOTE: (1) Stresses above these ratings may cause permanent damage. V– 4 5 Ref ELECTROSTATIC DISCHARGE SENSITIVITY PACKAGE/ORDERING INFORMATION This integrated circuit can be damaged by ESD. Burr-Brown PACKAGE recommends that all integrated circuits be handled with ap- DRAWING TEMPERATURE PRODUCT PACKAGE NUMBER(1) RANGE propriate precautions. Failure to observe proper handling and INA131AP 8-Pin Plastic DIP 006 –40(cid:176)C to +85(cid:176)C installation procedures can cause damage. INA131BP 8-Pin Plastic DIP 006 –40(cid:176)C to +85(cid:176)C ESD damage can range from subtle performance degradation NOTE: (1) For detailed drawing and dimension table, please see end of data to complete device failure. Precision integrated circuits may sheet, or Appendix C of Burr-Brown IC Data Book. be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. ® 3 INA131

TYPICAL PERFORMANCE CURVES At 25(cid:176)C, V = – 15V, unless otherwise noted. S GAIN vs FREQUENCY COMMON-MODE REJECTION vs FREQUENCY 60 140 B) 120 d 40 on ( 100 cti B) eje 80 d R ain ( 20 ode 60 G M n- 0 mmo 40 o C 20 –20 0 100 1k 10k 100k 1M 10M 10 100 1k 10k 100k 1M Frequency (Hz) Frequency (Hz) INPUT COMMON-MODE VOLTAGE RANGE POWER SUPPLY REJECTION vs OUTPUT VOLTAGE vs FREQUENCY 15 140 n-Mode Voltage (V) 1500 A3+ L– iO mOuiutteptpduu tb tSyw AiVVn1DDVg//C22M ––++ + LOimuAtiVpt3eO u+dt SbOywu Atinp2gut upply Rejection (dB) 1186200000 PPPPoooossssiiiittttiiiivvvveeee SSSSuuuuppppppppllllyyyy Negative Supply o –5 Swing Limit Swing Limit S Comm –10 – LOimutipteudt Sbyw Ain2g –L iOmuittepdu tb Syw Ain1g Power 4200 –15 0 –15 –10 –5 0 5 10 15 10 100 1k 10k 100k 1M Output Voltage (V) Frequency (Hz) INPUT- REFERRED NOISE VOLTAGE vs FREQUENCY OFFSET VOLTAGE WARM-UP vs TIME 100 6 z) H (cid:214)Referred Noise Voltage (nV/ 10 Offset Voltage Change (µV) ––42024 ut- p n I 1 –6 1 10 100 1k 10k 0 15 30 45 60 75 90 105 120 Frequency (Hz) Time from Power Supply Turn-on (s) ® INA131 4

TYPICAL PERFORMANCE CURVES (CONT) At 25(cid:176)C, V = – 15V, unless otherwise noted. S INPUT BIAS AND INPUT OFFSET CURRENT INPUT BIAS CURRENT vs TEMPERATURE vs INPUT VOLTAGE 2 3 A) n nt ( 2 e Curr 1 mA) s and Input Offset –01 ±IIBOS nput Bias Current ( –101 Co(|mIBm1| o+n |-IMB2o|)de Differential Mode a I Bi –2 ut p n I –2 –3 –40 –15 10 35 60 85 –45 –30 –15 0 15 30 45 Temperature (°C) Differential Overload Voltage (V) MAXIMUM OUTPUT SWING vs FREQUENCY SLEW RATE vs TEMPERATURE 32 1.2 28 V) 1.0 e ( 24 ud s) plit 20 V/µ 0.8 Am e ( k 16 at a R ak-to-Pe 128 Slew 0.6 e 0.4 P 4 0 0.2 10 100 1k 10k 100k 1M –75 –50 –25 0 25 50 75 100 125 Frequency (Hz) Temperature (°C) OUTPUT CURRENT LIMIT vs TEMPERATURE QUIESCENT CURRENT vs TEMPERATURE 30 2.8 mA) 25 A) 2.6 Circuit Current ( 20 +|ICL| scent Current (m 22..42 hort 15 Quie S –|I | 2.0 CL 10 1.8 –40 –15 10 35 60 85 –75 –50 –25 0 25 50 75 100 125 Temperature (°C) Temperature (°C) ® 5 INA131

TYPICAL PERFORMANCE CURVES (CONT) At 25(cid:176)C, V = – 15V, unless otherwise noted. S QUIESCENT CURRENT AND POWER DISSIPATION vs POWER SUPPLY VOLTAGE POSITIVE SIGNAL SWING vs TEMPERATUE (R = 2kW ) L 2.6 120 16 V = ±15V S 14 2.5 100 A) W) 12 ent (m 2.4 Power Dissipation 80 on (m ge (V) 10 VS = ±11.4V Quiescent Curr 22..32 Quiescent Current 6400 Power Dissipati Output Volta 864 2.1 20 V = ±2.25V 2 S 2.0 0 0 0 ±3 ±6 ±9 ±12 ±15 ±18 –75 –50 –25 0 25 50 75 100 125 Power Supply Voltage (V) Temperature (°C) NEGATIVE SIGNAL SWING vs TEMPERATUE (R = 2kW ) LARGE SIGNAL RESPONSE, G = 100 L –16 V = ±15V S –14 –12 +10V V) VS = ±11.4V e ( –10 g a olt –8 0 V ut p –6 ut O –4 –10V V = ±2.25V S –2 0 –75 –50 –25 0 25 50 75 100 125 Temperature (°C) SMALL SIGNAL RESPONSE, G = 100 INPUT-REFERRED NOISE, 0.1 to 10Hz +200mV 0 0.1m V/div –200mV 1s/div ® INA131 6

APPLICATION INFORMATION device. Absolute accuracy of the internal values is – 40%. The nominal gain with an external R resistor can be G Figure 1 shows the basic connections required for operation calculated by: of the INA131. Applications with noisy or high impedance power supplies may require decoupling capacitors close to G=100+ 250kW (1) the device pins as shown. R G The output is referred to the output reference (Ref) terminal which is normally grounded. This must be a low-impedance Where: R is the external gain resistor. connection to assure good common-mode rejection. A resis- G Accuracy of the 250kW term is – 40%. tance of 5W in series with the Ref pin will cause a device with 110dB CMR to degrade to approximately 106dB CMR. The stability and temperature drift of the external gain setting resistor, R also affects gain. R ’s contribution to SETTING THE GAIN G, G gain accuracy and drift can be directly inferred from the No external resistors are required for G = 100. On-chip gain equation (1). laser-trimmed resistors set the gain, providing excellent gain accuracy and temperature stability. Gain is distributed be- tween the input and output stages of the INA131. Bandwidth NOISE PERFORMANCE is increased by approximately five times (compared to the The INA131 provides very low noise in most applications. INA114 in G = 100). Input common-mode range is also For differential source impedances less than 1kW , the improved (see “Input Common-Mode Range”). INA103 may provide lower noise. For source impedances greater than 50kW , the INA111 FET-Input Instrumentation Although the INA131 is primarily intended for fixed Amplifier may provide lower noise. G = 100 applications, the gain can be increased by connect- ing an external resistor to the R pins. The internal resistors Low frequency noise of the INA131 is approximately G are trimmed for precise ratios, not to absolute values, so the 0.4m Vp-p measured from 0.1 to 10Hz. This is approxi- influence of an external resistor will vary from device to mately one-tenth the noise of state-of-the-art chopper-stabi- lized amplifiers. V+ 0.1µF Pin numbers are for DIP packages. 7 INA131 – 2 Over-Voltage V IN Protection A 1 5kW 25kW 1 25kW V = 100 • (V+ – V–) O IN IN 6 2.63kW A3 + 8 25kW Load VO – 5 A + 3 Over-Voltage 2 V 5kW 25kW IN Protection 4 0.1µF Also drawn in simplified form: V– V– IN INA131 V O V+ Ref IN FIGURE 1. Basic Connections. ® 7 INA131

OFFSET TRIMMING The INA131 is laser trimmed for very low offset voltage and Microphone, drift. Most applications require no external offset adjust- Hydrophone INA131 ment. Figure 2 shows an optional circuit for trimming the etc. output offset voltage. The voltage applied to Ref terminal is summed at the output. Low impedance must be maintained 47kW 47kW at this node to assure good common-mode rejection. This is achieved by buffering trim voltage with an op amp as shown. Thermocouple INA131 – V+ VIN VO INA131 + 100µA 10kW VIN Ref 1/2 REF200 100W OPA177 ±10mV 10kW INA131 Adjustment Range 100W Center-tap provides 100µA bias current return. 1/2 REF200 FIGURE 3. Providing an Input Common-Mode Current Path. V– FIGURE 2. Optional Trimming of Output Offset Voltage. INA114 and other unity output gain instrumentation ampli- fiers, the INA131 provides several additional volts of input INPUT BIAS CURRENT RETURN PATH common-mode range with full output voltage swing. See the typical performance curve “Input Common-Mode Range vs The input impedance of the INA131 is extremely high— approximately 1010W . However, a path must be provided for Output Voltage”. the input bias current of both inputs. This input bias current Input-overload often produces an output voltage that appears is typically less than – 1nA (it can be either polarity due to normal. For example, an input voltage of +20V on one input cancellation circuitry). High input impedance means that and +40V on the other input will obviously exceed the linear this input bias current changes very little with varying input common-mode range of both input amplifiers. Since both voltage. input amplifiers are saturated to the nearly the same output voltage limit, the difference voltage measured by the output Input circuitry must provide a path for this input bias current amplifier will be near zero. The output of the INA131 will if the INA131 is to operate properly. Figure 3 shows various be near 0V even though both inputs are overloaded. provisions for an input bias current path. Without a bias current return path, the inputs will float to a potential which exceeds the common-mode range of the INA131 and the INPUT PROTECTION input amplifiers will saturate. If the differential source resis- The inputs of the INA131 are individually protected for tance is low, bias current return path can be connected to one voltages up to – 40V. For example, a condition of –40V on input (see thermocouple example in Figure 3). With higher one input and +40V on the other input will not cause source impedance, using two resistors provides a balanced damage. Internal circuitry on each input provides low series input with possible advantages of lower input offset voltage impedance under normal signal conditions. To provide due to bias current and better common-mode rejection. equivalent protection, series input resistors would contribute excessive noise. If the input is overloaded, the protection INPUT COMMON-MODE RANGE circuitry limits the input current to a safe value (approxi- mately 1.5mA). The typical performance curve “Input Bias The linear common-mode range of the input op amps of the INA131 is approximately – 13.75V (or 1.25V from the Current vs Input Voltage” shows this input current limit behavior. The inputs are protected even if no power supply power supplies). As the output voltage increases, however, voltage is present. the linear input range is limited by the output voltage swing of the input amplifiers, A and A. The 5V/V output stage 1 2 gain of the INA131 reduces this effect. Compared to the ® INA131 8

VI–N 1MW VO V+ 1MW INA131 IN Ref Shield is driven at the common-mode potential. 100W Common-mode resistors have OPA602 approximately 0.1% effect on gain. FIGURE 4. Shield Driver Circuit. V+ V+ REF200 Equal line resistance here creates 100µA a small common-mode voltage which is rejected by INA131. 1 V O RTD INA131 2 Ref R Z 3 Resistance in this line causes VO = 0V at RRTD = RZ a small common-mode voltage which is rejected by INA131. FIGURE 5. RTD Temperature Measurement Circuit. V+ 2 10.0V 6 REF102 R 1 R 27kW 4 80.6kW 4 1N4148 (2) (1) R2 R7 Cu 5.23kW 1MW V O INA131 K Cu Ref R3 R5 100W 50W R 6 SEEBECK 100W ISA COEFFICIENT R R TYPE MATERIAL (m V/(cid:176)C) (R = 1200W ) (R + R 4= 100W ) Zero Adj 3 5 6 E Chromel 58.5 3.48kW 56.2kW Constantan J Iron 50.2 4.12kW 64.9kW Constantan K Chromel 39.4 5.23kW 80.6kW Alumel T Copper 38.0 5.49kW 84.5kW Constantan NOTES: (1) –2.1mV/(cid:176)C at 200m A. (2) R provides down-scale burn-out indication. 7 FIGURE 6. Thermocouple Amplifier with Cold Junction Compensation. ® 9 INA131

+10V – R I = 1 0 0 • VIN O R VIN INA131 + Ref Bridge I B V O INA131 A1 IO Ref Load FIGURE 7. Bridge Transducer Amplifier. A I Error 1 B OPA177 – 1.5nA OPA602 1pA OPA128 75fA – V O VIN INA131 + FIGURE 9. Differential Voltage to Current Converter. Ref R C 1 1 1MW 0.1µF f = 1 OPA602 –3dB 2p R1C1 = 1.59Hz FIGURE 8. AC-Coupled Instrumentation Amplifier. ® INA131 10

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