® INA131 INA 131 Precision G = 100 INSTRUMENTATION AMPLIFIER FEATURES DESCRIPTION ● LOW OFFSET VOLTAGE: 50µV max ● LOW DRIFT: 0.25µV/°C max The INA131 is a low cost, general purpose G = 100 instrumentation amplifier offering excellent accuracy. Its 3-op amp design and small size make it ideal for a wide range of applications. ● LOW INPUT BIAS CURRENT: 2nA max ● HIGH COMMON-MODE REJECTION: 110dB min ● INPUT OVERVOLTAGE PROTECTION: ±40V ● WIDE SUPPLY RANGE: ±2.25 to ±18V ● LOW QUIESCENT CURRENT: 3mA ● 8-PIN PLASTIC DIP On-chip laser trimmed resistors accurately set a fixed gain of 100. The INA131 is laser trimmed to achieve very low offset voltage (50µV max), drift (0.25µV/°C max), and high CMR (110dB min). Internal input protection can withstand up to ±40V inputs without damage. The INA131 is available in a 8-pin plastic DIP. They are specified over the –40°C to +85°C temperature range. APPLICATIONS ● ● ● ● ● BRIDGE AMPLIFIER THERMOCOUPLE AMPLIFIER RTD SENSOR AMPLIFIER MEDICAL INSTRUMENTATION DATA ACQUISITION V+ 7 – VIN 2 Over-Voltage Protection INA131 A1 5kΩ 1 25kΩ 25kΩ A3 2.63kΩ 8 + VIN 3 6 + – VO = 100 (VIN – VIN) 25kΩ Over-Voltage Protection 5 A2 5kΩ Ref 25kΩ 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 SPECIFICATIONS At TA = +25°C, VS = ±15V, RL = 2kΩ, unless otherwise noted. INA131BP PARAMETER CONDITIONS INPUT Offset Voltage, RTI Initial vs Temperature vs Power Supply Long-Term Stability Impedance, Differential Common-Mode Input Common-Mode Range Safe Input Voltage Common-Mode Rejection TYP MAX ±50 ±0.25 3 ±11 ±10 ±0.1 0.5 0.2 1010 || 6 1010 || 6 ±13.5 110 120 TA = +25°C TA = TMIN to TMAX VS = ±2.25V to ±18V VCM = ±10V, ∆RS = 1kΩ INA131AP MIN MIN TYP MAX UNITS ±125 ±1 ✻ ✻ ±25 ±0.25 ✻ ✻ ✻ ✻ ✻ 106 110 µV µV/°C µV/V µV/mo Ω || pF Ω || pF V V dB ±40 ✻ BIAS CURRENT vs Temperature ±0.5 ±8 ±2 ✻ ✻ ±5 nA pA/°C OFFSET CURRENT vs Temperature ±0.5 ±8 ±2 ✻ ✻ ±5 nA pA/°C NOISE VOLTAGE, RTI f = 10Hz f = 100Hz f = 1kHz f = 10kHz fB = 0.1Hz to 10Hz Noise Current f = 10Hz f= 1kHz fB = 0.1Hz to 100Hz RS = 0Ω GAIN Gain Error(1) Resistor Value(2) Gain vs Temperature Nonlinearity OUTPUT Voltage Load Capacitance, max Short Circuit Current FREQUENCY RESPONSE Bandwidth, –3dB Slew Rate Settling Time, 0.01% Overload Recovery POWER SUPPLY Voltage Range Current IO = 5mA, TMIN to TMAX VS = ±11.4V, RL = 2kΩ VS = ±2.25V, R L= 2kΩ Stable Operation ±13.5 ±10 ±1 VO = ±10V 0.3 50% Overdrive ±2.25 VIN = 0V TEMPERATURE RANGE Specification Operating θJA 16 12 12 12 0.4 ✻ ✻ ✻ ✻ ✻ nV/√Hz nV/√Hz nV/√Hz nV/√Hz µVp-p 0.4 0.2 18 ✻ ✻ ✻ pA/√Hz pA/√Hz pAp-p ±0.01 ±10 ±0.024 ±40 ✻ ✻ ±0.1 ✻ % % ±5 ±0.0003 ±10 ±0.002 ✻ ✻ ±20 ±0.004 ppm/°C % of FSR ±13.7 10.5 1.5 1000 +20/–15 ✻ ✻ ✻ 70 0.7 100 20 ±15 ±2.2 –40 –40 ✻ ±18 ±3 ✻ 85 125 ✻ ✻ 100 ✻ ✻ ✻ ✻ ✻ V V V pF mA ✻ ✻ ✻ ✻ kHz V/µs µs µs ✻ ✻ ✻ ✻ ✻ V mA ✻ ✻ °C °C °C/W ✻ Specification same as INA131BP. NOTES: (1) RL = 10kΩ. (2) Absolute value of internal gain-setting resistors. (Gain depends on resistor ratios.) 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 ABSOLUTE MAXIMUM RATINGS(1) PIN CONFIGURATION Top View P-Package/8-Pin DIP RG 1 8 RG V –IN 2 7 V+ V +IN 3 6 VO V– 4 5 Ref Supply Voltage .................................................................................. ±18V Input Voltage Range .......................................................................... ±40V Output Short Circuit (to ground) .............................................. Continuous Operating Temperature .................................................. –40°C to +125°C Storage Temperature ..................................................... –40°C to +125°C Junction Temperature .................................................................... +150°C Lead Temperature (soldering –10s) .............................................. +300°C NOTE: (1) Stresses above these ratings may cause permanent damage. ELECTROSTATIC DISCHARGE SENSITIVITY PACKAGE/ORDERING INFORMATION PRODUCT PACKAGE PACKAGE DRAWING NUMBER(1) INA131AP INA131BP 8-Pin Plastic DIP 8-Pin Plastic DIP 006 006 TEMPERATURE RANGE –40°C to +85°C –40°C to +85°C This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. ® 3 INA131 TYPICAL PERFORMANCE CURVES At 25°C, VS = ±15V, unless otherwise noted. COMMON-MODE REJECTION vs FREQUENCY GAIN vs FREQUENCY 60 Common-Mode Rejection (dB) 140 Gain (dB) 40 20 0 100 80 60 40 20 0 –20 100 1k 10k 100k 1M 10 10M 100 1k 100k Frequency (Hz) INPUT COMMON-MODE VOLTAGE RANGE vs OUTPUT VOLTAGE POWER SUPPLY REJECTION vs FREQUENCY 1M 140 VD/2 5 VD/2 0 Limited by A2 + Output Swing Power Supply Rejection (dB) by A 1 Limited g ut Swin tp u O + 10 – VO + – + VCM –5 –10 –15 –15 A3 – Output Swing Limit A3 + Output Swing Limit Limited by A 2 – Outpu t Swing by A 1 Limited g ut Swin – Outp Negative Supply 120 100 80 Positive Supply 60 40 20 0 –10 –5 0 5 10 15 10 100 1k Output Voltage (V) 10k 100k 1M Frequency (Hz) INPUT- REFERRED NOISE VOLTAGE vs FREQUENCY OFFSET VOLTAGE WARM-UP vs TIME 100 6 Offset Voltage Change (µV) Input-Referred Noise Voltage (nV/√ Hz) 10k Frequency (Hz) 15 Common-Mode Voltage (V) 120 10 1 4 2 0 –2 –4 –6 1 10 100 1k 10k 0 Frequency (Hz) 30 45 60 75 90 Time from Power Supply Turn-on (s) ® INA131 15 4 105 120 TYPICAL PERFORMANCE CURVES (CONT) At 25°C, VS = ±15V, unless otherwise noted. INPUT BIAS CURRENT vs INPUT VOLTAGE 2 3 2 Input Bias Current (mA) Input Bias and Input Offset Current (nA) INPUT BIAS AND INPUT OFFSET CURRENT vs TEMPERATURE 1 ±IB 0 IOS –1 1 0 Common-Mode (|IB1| + |IB2|) Differential Mode –1 –2 –2 –40 –15 10 35 60 –3 –45 85 –30 Temperature (°C) MAXIMUM OUTPUT SWING vs FREQUENCY 0 15 30 45 SLEW RATE vs TEMPERATURE 32 1.2 28 1.0 24 Slew Rate (V/µs) Peak-to-Peak Amplitude (V) –15 Differential Overload Voltage (V) 20 16 12 8 0.8 0.6 0.4 4 0 10 100 1k 10k 100k 0.2 –75 1M –50 –25 Frequency (Hz) OUTPUT CURRENT LIMIT vs TEMPERATURE 50 75 100 125 2.8 Quiescent Current (mA) Short Circuit Current (mA) 25 QUIESCENT CURRENT vs TEMPERATURE 30 25 +|ICL| 20 15 –|ICL| 10 –40 0 Temperature (°C) –15 10 35 60 2.6 2.4 2.2 2.0 1.8 –75 85 Temperature (°C) –50 –25 0 25 50 75 100 125 Temperature (°C) ® 5 INA131 TYPICAL PERFORMANCE CURVES (CONT) At 25°C, VS = ±15V, unless otherwise noted. POSITIVE SIGNAL SWING vs TEMPERATUE (RL = 2kΩ) 120 2.5 100 2.4 80 Power Dissipation 2.3 60 Quiescent Current 2.2 40 2.1 20 2.0 0 ±3 ±6 ±9 ±12 16 12 VS = ±11.4V 10 8 6 4 VS = ±2.25V 2 0 ±18 ±15 VS = ±15V 14 Output Voltage (V) 2.6 Power Dissipation (mW) Quiescent Current (mA) QUIESCENT CURRENT AND POWER DISSIPATION vs POWER SUPPLY VOLTAGE 0 –75 –50 –25 0 25 50 75 100 125 Temperature (°C) Power Supply Voltage (V) LARGE SIGNAL RESPONSE, G = 100 NEGATIVE SIGNAL SWING vs TEMPERATUE (RL = 2kΩ) –16 VS = ±15V Output Voltage (V) –14 –12 +10V VS = ±11.4V –10 0 –8 –6 –4 –10V VS = ±2.25V –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 0.1µV/div 0 –200mV 1s/div ® INA131 6 device. Absolute accuracy of the internal values is ±40%. The nominal gain with an external RG resistor can be calculated by: APPLICATION INFORMATION Figure 1 shows the basic connections required for operation of the INA131. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins as shown. G = 100 + 250 kΩ RG The output is referred to the output reference (Ref) terminal which is normally grounded. This must be a low-impedance connection to assure good common-mode rejection. A resistance of 5Ω in series with the Ref pin will cause a device with 110dB CMR to degrade to approximately 106dB CMR. (1) Where: RG is the external gain resistor. Accuracy of the 250kΩ term is ±40%. The stability and temperature drift of the external gain setting resistor, RG, also affects gain. RG’s contribution to gain accuracy and drift can be directly inferred from the gain equation (1). SETTING THE GAIN No external resistors are required for G = 100. On-chip laser-trimmed resistors set the gain, providing excellent gain accuracy and temperature stability. Gain is distributed between the input and output stages of the INA131. Bandwidth is increased by approximately five times (compared to the INA114 in G = 100). Input common-mode range is also improved (see “Input Common-Mode Range”). NOISE PERFORMANCE The INA131 provides very low noise in most applications. For differential source impedances less than 1kΩ, the INA103 may provide lower noise. For source impedances greater than 50kΩ, the INA111 FET-Input Instrumentation Amplifier may provide lower noise. Although the INA131 is primarily intended for fixed G = 100 applications, the gain can be increased by connecting an external resistor to the RG pins. The internal resistors are trimmed for precise ratios, not to absolute values, so the influence of an external resistor will vary from device to Low frequency noise of the INA131 is approximately 0.4µVp-p measured from 0.1 to 10Hz. This is approximately one-tenth the noise of state-of-the-art chopper-stabilized amplifiers. V+ 0.1µF Pin numbers are for DIP packages. – VIN 2 Over-Voltage Protection 7 INA131 A1 5kΩ 1 25kΩ + 25kΩ – ) VO = 100 • (VIN – VIN 6 A3 2.63kΩ + 8 25kΩ Load VO – + VIN 3 Over-Voltage Protection 5 A2 5kΩ 4 25kΩ 0.1µF Also drawn in simplified form: V– – VIN INA131 V+ IN VO Ref FIGURE 1. Basic Connections. ® 7 INA131 OFFSET TRIMMING The INA131 is laser trimmed for very low offset voltage and drift. Most applications require no external offset adjustment. Figure 2 shows an optional circuit for trimming the output offset voltage. The voltage applied to Ref terminal is summed at the output. Low impedance must be maintained at this node to assure good common-mode rejection. This is achieved by buffering trim voltage with an op amp as shown. Microphone, Hydrophone etc. INA131 47kΩ 47kΩ Thermocouple – VIN VO V+ INA131 + VIN 100µA 1/2 REF200 Ref OPA177 ±10mV Adjustment Range INA131 10kΩ 100Ω 10kΩ INA131 100Ω Center-tap provides bias current return. 100µA 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 amplifiers, the INA131 provides several additional volts of input common-mode range with full output voltage swing. See the typical performance curve “Input Common-Mode Range vs Output Voltage”. INPUT BIAS CURRENT RETURN PATH The input impedance of the INA131 is extremely high— approximately 1010Ω. However, a path must be provided for the input bias current of both inputs. This input bias current is typically less than ±1nA (it can be either polarity due to cancellation circuitry). High input impedance means that this input bias current changes very little with varying input voltage. Input-overload often produces an output voltage that appears normal. For example, an input voltage of +20V on one input and +40V on the other input will obviously exceed the linear common-mode range of both input amplifiers. Since both input amplifiers are saturated to the nearly the same output voltage limit, the difference voltage measured by the output amplifier will be near zero. The output of the INA131 will be near 0V even though both inputs are overloaded. Input circuitry must provide a path for this input bias current if the INA131 is to operate properly. Figure 3 shows various 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 amplifiers will saturate. If the differential source resistance is low, bias current return path can be connected to one input (see thermocouple example in Figure 3). With higher source impedance, using two resistors provides a balanced input with possible advantages of lower input offset voltage due to bias current and better common-mode rejection. INPUT PROTECTION The inputs of the INA131 are individually protected for voltages up to ±40V. For example, a condition of –40V on one input and +40V on the other input will not cause damage. Internal circuitry on each input provides low series impedance under normal signal conditions. To provide equivalent protection, series input resistors would contribute excessive noise. If the input is overloaded, the protection circuitry limits the input current to a safe value (approximately 1.5mA). The typical performance curve “Input Bias Current vs Input Voltage” shows this input current limit behavior. The inputs are protected even if no power supply voltage is present. INPUT COMMON-MODE RANGE The linear common-mode range of the input op amps of the INA131 is approximately ±13.75V (or 1.25V from the power supplies). As the output voltage increases, however, the linear input range is limited by the output voltage swing of the input amplifiers, A1 and A2. The 5V/V output stage gain of the INA131 reduces this effect. Compared to the ® INA131 8 – VIN 1MΩ 1MΩ + VIN VO INA131 Ref Shield is driven at the common-mode potential. 100Ω Common-mode resistors have approximately 0.1% effect on gain. OPA602 FIGURE 4. Shield Driver Circuit. V+ V+ REF200 100µA Equal line resistance here creates a small common-mode voltage which is rejected by INA131. 1 RTD VO INA131 2 Ref RZ 3 VO = 0V at RRTD = RZ Resistance in this line causes a small common-mode voltage which is rejected by INA131. FIGURE 5. RTD Temperature Measurement Circuit. V+ 2 10.0V 6 REF102 R1 27k Ω 1N4148 (1) Cu R2 5.23k Ω R4 80.6k Ω 4 (2) R7 1MΩ INA131 K Cu Ref R3 100Ω ISA TYPE MATERIAL SEEBECK COEFFICIENT (µV/°C) R2 (R3 = 100Ω) R4 (R5 + R6 = 100Ω) E Chromel Constantan 58.5 3.48kΩ 56.2kΩ J Iron Constantan 50.2 4.12kΩ 64.9kΩ K Chromel Alumel 39.4 5.23kΩ 80.6kΩ T Copper Constantan 38.0 5.49kΩ 84.5kΩ VO R5 50Ω R6 100Ω Zero Adj NOTES: (1) –2.1mV/°C at 200µA. (2) R7 provides down-scale burn-out indication. FIGURE 6. Thermocouple Amplifier with Cold Junction Compensation. ® 9 INA131 +10V – VIN R IO = 100 • VIN R INA131 + Ref Bridge IB VO INA131 A1 Ref IO Load FIGURE 7. Bridge Transducer Amplifier. – VIN + ±1.5nA 1pA 75fA FIGURE 9. Differential Voltage to Current Converter. C1 0.1µF OPA602 R1 1MΩ f–3dB = 1 2πR1C1 = 1.59Hz FIGURE 8. AC-Coupled Instrumentation Amplifier. ® INA131 IB Error OPA177 OPA602 OPA128 VO INA131 Ref A1 10