INA1 ® INA111 11 INA1 11 High Speed FET-Input INSTRUMENTATION AMPLIFIER FEATURES DESCRIPTION ● FET INPUT: IB = 20pA max The INA111 is a high speed, FET-input instrumentation amplifier offering excellent performance. ● LOW OFFSET VOLTAGE: 500µV max ● LOW OFFSET VOLTAGE DRIFT: 5µV/°C max The INA111 uses a current-feedback topology providing extended bandwidth (2MHz at G = 10) and fast settling time (4µs to 0.01% at G = 100). A single external resistor sets any gain from 1 to over 1000. ● HIGH SPEED: TS = 4µs (G = 100, 0.01%) ● HIGH COMMON-MODE REJECTION: 106dB min Offset voltage and drift are laser trimmed for excellent DC accuracy. The INA111’s FET inputs reduce input bias current to under 20pA, simplifying input filtering and limiting circuitry. ● 8-PIN PLASTIC DIP, SOL-16 SOIC The INA111 is available in 8-pin plastic DIP, and SOL-16 surface-mount packages, specified for the –40°C to +85°C temperature range. APPLICATIONS ● MEDICAL INSTRUMENTATION ● DATA ACQUISITION V+ 7 (13) INA111 – VIN 2 (4) Feedback A1 10kΩ 1 10kΩ A3 RG 8 VIN 6 (11) VO G=1+ 25kΩ (15) 3 DIP Connected Internally 25kΩ (2) + (12) 5 A2 10kΩ (5) 10kΩ (10) 50kΩ RG Ref 4 (7) DIP (SOIC) 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-1143E 1 INA111 Printed in U.S.A. March, 1998 SPECIFICATIONS ELECTRICAL At TA = +25°C, VS = ±15V, RL = 2kΩ, unless otherwise noted. INA111BP, BU PARAMETER CONDITIONS INPUT Offset Voltage, RTI Initial TA = +25°C vs Temperature TA = TMIN to TMAX vs Power Supply VS = ±6V to ±18V Impedance, Differential Common-Mode Input Common-Mode Range VDIFF = 0V Common-Mode Rejection VCM = ±10V, ∆RS = 1kΩ G=1 G = 10 G = 100 G = 1000 TYP MAX ±500 ± 2000/G ±5 ± 100/G 30 + 100/G ±10 ±100 ± 500/G ±2 ± 10/G 2 +10/G 1012 || 6 1012 || 3 ±12 80 96 106 106 90 110 115 115 BIAS CURRENT OFFSET CURRENT MIN TYP MAX UNITS ±1000 ± 5000/G ±10 ± 100/G ✻ ✻ ±200 ± 500/G ±2 ± 20/G ✻ ✻ ✻ ✻ µV µV/°C µV/V Ω || pF Ω || pF V 75 90 100 100 ✻ ✻ ✻ ✻ ±2 ±20 ✻ ✻ pA ±0.1 ±10 ✻ ✻ pA 13 10 10 1 ✻ ✻ ✻ ✻ nV/√Hz nV/√Hz nV/√Hz µVp-p 0.8 ✻ fA/√Hz ✻ 1 + (50kΩ/RG) 1 Gain vs Temperature 50kΩ Resistance(1) G = 1, RL = 10kΩ G = 10, RL = 10kΩ G = 100, RL = 10kΩ G = 1000, RL = 10kΩ G=1 ±0.01 ±0.1 ±0.15 ±0.25 ±1 ±25 10000 ±0.02 ±0.5 ±0.5 ±1 ±10 ±100 G=1 G = 10 G = 100 G = 1000 ±0.0005 ±0.001 ±0.001 ±0.005 ±0.005 ±0.005 ±0.005 ±0.02 Nonlinearity OUTPUT Voltage Load Capacitance Stability Short Circuit Current FREQUENCY RESPONSE Bandwidth, –3dB IO = 5mA, TMIN to TMAX Overload Recovery G=1 G = 10 G = 100 G = 1000 VO = ±10V, G = 2 to 100 G=1 G = 10 G = 100 G = 1000 50% Overdrive POWER SUPPLY Voltage Range Current VIN = 0V Slew Rate Settling Time, 0.01% dB dB dB dB G = 1000, RS = 0Ω NOISE VOLTAGE, RTI f = 100Hz f = 1kHz f = 10kHz fB = 0.1Hz to 10Hz Noise Current f = 10kHz GAIN Gain Equation Range of Gain Gain Error INA111AP, AU MIN ±11 ✻ 2 2 450 50 17 2 2 4 30 1 ±6 TEMPERATURE RANGE Specification Operating θJA ±12.7 1000 +30/–25 ✻ ±15 ±3.3 –40 –40 ±18 ±4.5 ✻ 85 125 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ 0.05 ✻ ±0.7 ±2 ✻ ✻ ✻ ✻ ✻ ✻ ✻ ±0.01 ±0.01 ±0.04 % % % % of of of of FSR FSR FSR FSR ✻ ✻ ✻ V pF mA ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ ✻ MHz MHz kHz kHz V/µs µs µs µs µs µs ✻ ✻ ✻ 100 V/V V/V % % % % ppm/°C ppm/°C ✻ ✻ V mA ✻ ✻ °C °C °C/W ✻ Specification same as INA111BP. NOTE: (1) Temperature coefficient of the “50kΩ” term in the gain equation. 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. ® INA111 2 ELECTROSTATIC DISCHARGE SENSITIVITY PIN CONFIGURATIONS Top View DIP RG 1 8 RG V–IN 2 7 V+ + IN 3 6 VO V– 4 5 Ref V Top View 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. SOL-16 Surface Mount NC 1 16 NC RG 2 15 RG NC 3 14 NC V–IN 4 13 V+ V+IN 5 12 Feedback NC 6 11 VO V– 7 10 Ref NC 8 9 ORDERING INFORMATION PRODUCT PACKAGE INA111AP INA111BP INA111AU INA111BU 8-Pin Plastic DIP 8-Pin Plastic DIP SOL-16 Surface-Mount SOL-16 Surface-Mount TEMPERATURE RANGE –40°C –40°C –40°C –40°C to to to to +85°C +85°C +85°C +85°C PACKAGE INFORMATION NC PRODUCT INA111AP INA111BP INA111AU INA111BU ABSOLUTE MAXIMUM RATINGS(1) PACKAGE 8-Pin Plastic 8-Pin Plastic 16-Pin Surface 16-Pin Surface PACKAGE DRAWING NUMBER(1) DIP DIP Mount Mount 006 006 211 211 NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. Supply Voltage .................................................................................. ±18V Input Voltage Range .......................................... (V–) –0.7V to (V+) +15V 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: Stresses above these ratings may cause permanent damage. ® 3 INA111 TYPICAL PERFORMANCE CURVES At TA = +25°C, VS = ±15V, unless otherwise noted. GAIN vs FREQUENCY COMMON-MODE REJECTION vs FREQUENCY 10k 120 Common-Mode Rejection (dB) G = 1k Gain (V/V) 1k G = 100 100 G = 10 10 G=1 1 100 80 G = 1k 60 G = 100 40 G = 10 20 G=1 0 0.1 1k 10k 100k 1M 10 10M 100 1k INPUT COMMON-MODE VOLTAGE RANGE vs OUTPUT VOLTAGE 1M 120 y A1 ed b Limit ut Swing tp + Ou VD/2 10 5 – VO + – VD/2 0 Limit + Ou ed by A tput Swin2 g Power Supply Rejection (dB) Common-Mode Voltage (V) 100k POWER SUPPLY REJECTION vs FREQUENCY 15 + VCM (Any Gain) A3 – Output Swing Limit –5 A3 + Output Swing Limit Lim it – O ed by utpu A t Sw 2 ing –10 –15 –15 by A 1 g in ited Lim put Sw t u O – 100 80 G = 1k 60 G = 100 40 G = 10 G=1 20 0 –10 –5 0 5 10 10 15 100 1k 10k 100k 1M Frequency (Hz) Output Voltage (V) INPUT-REFERRED NOISE VOLTAGE vs FREQUENCY SETTLING TIME vs GAIN 1k 100 100 G=1 G = 10 G = 100, 1k 10 Settling Time (µs) Input-Referred Noise Voltage (nV/√Hz) 10k Frequency (Hz) Frequency (Hz) 0.01% 10 0.1% 1 1 1 10 100 1k 10k 1 ® INA111 10 100 Gain (V/V) Frequency (Hz) 4 1000 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, unless otherwise noted. INPUT BIAS CURRENT vs TEMPERATURE 50 200 25 100 0 0 G ≥ 10 –100 –25 G=1 –200 –50 10n 0 1 –10m 2 3 4 –75 –25 0 25 50 75 100 Temperature (°C) INPUT BIAS CURRENT vs DIFFERENTIAL INPUT VOLTAGE INPUT BIAS CURRENT vs COMMON-MODE INPUT VOLTAGE 125 –10m –15.7V Input Bias Current (A) –10µ G = 10 G = 100 G = 1k +1p G=1 G = 10 +10p G = 1k –5 0 –100µ –10µ +1p +15.7V +15.7V –10 –1m G = 100 +100p 5 10 15 +10p 20 –20 –15 Differential Overload Voltage (V) NOTE: One input grounded. –10 –5 0 5 10 15 20 Common-Mode Voltage (V) OUTPUT CURRENT LIMIT vs TEMPERATURE MAXIMUM OUTPUT VOLTAGE SWING vs FREQUENCY 50 30 25 Short-Circuit Current (mA) Peak-to-Peak Amplitude (V) Input Bias Current (A) –50 Time From Power Supply Turn-On (Minutes) –100µ –15 1p 0.01p –1m –20 10p 5 –15.7V G=1 IOS 100p 0.1p –300 –75 Ib 1n Input Bias Current (A) 300 Referred-to-Input VOS Change (µV) Referred-to-Input VOS Change (µV) OFFSET VOLTAGE WARM-UP vs TIME 75 20 15 10 5 0 40 30 +ICL –ICL 20 10 0 1k 10k 100k 1M –75 10M –50 –25 0 25 50 75 100 125 Temperature (°C) Frequency (Hz) ® 5 INA111 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, unless otherwise noted. TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY QUIESCENT CURRENT vs TEMPERATURE 1 3.5 3.4 G = 1k 0.1 THD + N (%) Quiescent Current (mA) VO = 3Vrms, RL = 2kΩ Measurement BW = 80kHz 3.3 3.2 Single-Ended Drive G = 1 G = 100 0.01 G = 10 0.001 Differential Drive G = 1 3.1 0.0001 3.0 –75 –50 –25 0 25 50 75 100 20 125 100 1k 10k 20k Frequency (Hz) Temperature (°C) LARGE SIGNAL RESPONSE, G = 100 SMALL SIGNAL RESPONSE, G = 1 +10 +0.1 0 0 –0.1 –10 0 10 0 20 10 Time (µs) Time (µs) LARGE SIGNAL RESPONSE, G = 100 SMALL SIGNAL RESPONSE, G = 1 +10 +0.1 0 0 –10 –0.1 0 10 20 0 Time (µs) ® INA111 10 Time (µs) 6 20 20 APPLICATION INFORMATION The 50kΩ term in equation 1 comes from the sum of the two internal feedback resistors. These are on-chip metal film resistors which are laser trimmed to accurate absolute values. The accuracy and temperature coefficient of these resistors are included in the gain accuracy and drift specifications of the INA111. Figure 1 shows the basic connections required for operation of the INA111. Applications with noisy or high impedance power supplies may require decoupling capacitors close to the device pins as shown. 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 2Ω in series with the Ref pin will cause a typical device with 90dB CMR to degrade to approximately 80dB CMR (G = 1). 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). Low resistor values required for high gain can make wiring resistance important. Sockets add to the wiring resistance, which will contribute additional gain error (possibly an unstable gain error) in gains of approximately 100 or greater. SETTING THE GAIN Gain of the INA111 is set by connecting a single external resistor, RG: G = 1 + 5 0kΩ RG DYNAMIC PERFORMANCE The typical performance curve “Gain vs Frequency” shows that the INA111 achieves wide bandwidth over a wide range of gain. This is due to the current-feedback topology of the INA111. Settling time also remains excellent over wide gains. (1) Commonly used gains and resistor values are shown in Figure 1. V+ 0.1µF Pin numbers are for DIP package. – VIN 7 INA111 2 A1 10kΩ 1 + – ) VO = G • (VIN – VIN 10kΩ 50kΩ G=1+ RG 25kΩ 6 A3 RG + 8 25kΩ Load VO – + VIN 3 5 A2 10kΩ 4 DESIRED GAIN 1 2 5 10 20 50 100 200 500 1000 2000 5000 10000 RG (Ω) NEAREST 1% RG (Ω) No Connection 50.00k 12.50k 5.556k 2.632k 1.02k 505.1 251.3 100.2 50.05 25.01 10.00 5.001 No Connection 49.9k 12.4k 5.62k 2.61k 1.02k 511 249 100 49.9 24.9 10 4.99 Ref 10kΩ 0.1µF Also drawn in simplified form: V– – VIN RG + VIN INA111 VO Ref FIGURE 1. Basic Connections ® 7 INA111 INPUT BIAS CURRENT RETURN PATH The INA111 exhibits approximately 6dB rise in gain at 2MHz in unity gain. This is a result of its current-feedback topology and is not an indication of instability. Unlike an op amp with poor phase margin, the rise in response is a predictable +6dB/octave due to a response zero. A simple pole at 700kHz or lower will produce a flat passband response (see Input Filtering). The input impedance of the INA111 is extremely high— approximately 1012Ω. However, a path must be provided for the input bias current of both inputs. This input bias current is typically less than 10pA. High input impedance means that this input bias current changes very little with varying input voltage. The INA111 provides excellent rejection of high frequency common-mode signals. The typical performance curve, “Common-Mode Rejection vs Frequency” shows this behavior. If the inputs are not properly balanced, however, common-mode signals can be converted to differential sig– + nals. Run the VIN and VIN connections directly adjacent each other, from the source signal all the way to the input pins. If possible use a ground plane under both input traces. Avoid running other potentially noisy lines near the inputs. Input circuitry must provide a path for this input bias current if the INA111 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 INA111 and the input amplifiers will saturate. If the differential source resistance is low, the bias current return path can be connected to one input (see the 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 high-frequency common-mode rejection. NOISE AND ACCURACY PERFORMANCE The INA111’s FET input circuitry provides low input bias current and high speed. It achieves lower noise and higher accuracy with high impedance sources. With source impedances of 2kΩ to 50kΩ the INA114 may provide lower offset voltage and drift. For very low source impedance (≤1kΩ), the INA103 may provide improved accuracy and lower noise. Crystal or Ceramic Transducer OFFSET TRIMMING INA111 1MΩ The INA111 is laser trimmed for 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. The op amp shown maintains low output impedance at high frequency. Trim circuits with higher source impedance should be buffered with an op amp follower circuit to assure low impedance on the Ref pin. 1MΩ Thermocouple INA111 10kΩ INA111 – VIN V+ VO RG INA111 + VIN 100µA 1/2 REF200 Ref OPA177 ±10mV Adjustment Range Center-tap provides bias current return. 100Ω(1) 10kΩ FIGURE 3. Providing an Input Common-Mode Current Path. (1) INPUT COMMON-MODE RANGE 100Ω(1) The linear common-mode range of the input op amps of the INA111 is approximately ±12V (or 3V from the power supplies). As the output voltage increases, however, the linear input range will be limited by the output voltage swing of the input amplifiers, A1 and A2. The common-mode range is related to the output voltage of the complete amplifier— see performance curve “Input Common-Mode Range vs Output Voltage”. 100µA 1/2 REF200 NOTE: (1) For wider trim range required in high gains, scale resistor values larger V– FIGURE 2. Optional Trimming of Output Offset Voltage. ® INA111 8 the 1N4148 may have leakage currents far greater than the input bias current of the INA111 and are usually sensitive to light. A combination of common-mode and differential input voltage can cause the output of A1 or A2 to saturate. Figure 4 shows the output voltage swing of A1 and A2 expressed in terms of a common-mode and differential input voltages. For applications where input common-mode range must be maximized, limit the output voltage swing by connecting the INA111 in a lower gain (see performance curve “Input Common-Mode Voltage Range vs Output Voltage”). If necessary, add gain after the INA111 to increase the voltage swing. INPUT FILTERING The INA111’s FET input allows use of an R/C input filter without creating large offsets due to input bias current. Figure 6 shows proper implementation of this input filter to preserve the INA111’s excellent high frequency commonmode rejection. Mismatch of the common-mode input capacitance (C1 and C2), either from stray capacitance or Input-overload often produces an output voltage that appears normal. For example, consider an input voltage of +14V on one input and +15V 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 INA111 will be near 0V even though both inputs are overloaded. V+ D1 D2 – VIN R1 INPUT PROTECTION Inputs of the INA111 are protected for input voltages from 0.7V below the negative supply to 15V above the positive power supply voltages. If the input current is limited to less than 1mA, clamp diodes are not required; internal junctions will clamp the input voltage to safe levels. If the input source can supply more than 1mA, use external clamp diodes as shown in Figure 5. The source current can be limited with series resistors R1 and R2 as shown. Resistor values greater than 10kΩ will contribute noise to the circuit. + VIN INA111 RG R2 D3 VO D4 V+ Diodes: 2N4117A 1pA Leakage = A diode formed with a 2N4117A transistor as shown in Figure 5 assures low leakage. Common signal diodes such as FIGURE 5. Input Protection Voltage Clamp. VCM – V+ G • VD 2 INA111 A1 10kΩ VD 2 10kΩ 25kΩ A3 RG G=1+ 50kΩ RG VO = G • VD 25kΩ VD 2 A2 10kΩ VCM VCM + G • VD 2 10kΩ V– FIGURE 4. Voltage Swing of A1 and A2. ® 9 INA111 mismatched values, causes a high frequency common-mode signal to be converted to a differential signal. This degrades common-mode rejection. The differential input capacitor, C3, reduces the bandwidth and mitigates the effects of mismatch in C1 and C2. Make C3 much larger than C1 and C2. If properly matched, C1 and C2 also improve CMR. Surface-mount package version only. – VIN RG OUTPUT VOLTAGE SENSE (SOL-16 Package Only) INA111 Ref + VIN The surface-mount version of the INA111 has a separate output sense feedback connection (pin 12). Pin 12 must be connected, usually to the output terminal, pin 11, for proper operation. (This connection is made internally on the DIP version of the INA111.) C1 1000pF Feedback Load Equal resistance here preserves good common-mode rejection. FIGURE 8. Remote Load and Ground Sensing. The output feedback connection can be used to sense the output voltage directly at the load for best accuracy. Figure 8 shows how to drive a load through series interconnection resistance. Remotely located feedback paths may cause instability. This can be generally be eliminated with a high frequency feedback path through C1. C1 VO INA111 RG C2 Ref R1 f−3 d B = C1 – R1 1 C 4 π R1 C 3 + 1 2 VO INA111 C3 R2 fc = 1 2πR1C1 NOTE: To preserve good low frequency CMR, make R1 = R2 and C1 = C2. VIN + VIN R2 FIGURE 9. High-Pass Input Filter. Ref C2 R1 = R2 C1 = C2 C3 ≈ 10C1 ±6V to ±18V Isolated Power V+ V– ±15V FIGURE 6. Input Low-Pass Filter. – VIN INA111 ISO122 VO +10V + VIN Ref G = 500 Bridge RG 100Ω INA111 VO Isolated Common Ref FIGURE 10. Galvanically Isolated Instrumentation Amplifier. FIGURE 7. Bridge Transducer Amplifier. ® INA111 10 VIN OPA177 – VIN + RG INA111 Ref C1 50nF VO R1 1MΩ C1 0.1µF R1 10kΩ RG INA111 1 f–3dB = 2πR1C1 OPA602 R2 Ref IL = = 1.59Hz Load Make G ≤ 10 where G = 1 + 50k RG FIGURE 11. AC-Coupled Instrumentation Amplifier. VIN G • R2 FIGURE 12. Voltage Controlled Current Source. – VIN 22.1kΩ 22.1kΩ + VIN 511Ω VO INA111 Ref 100Ω NOTE: Driving the shield minimizes CMR degradation due to unequally distributed capacitance on the input line. The shield is driven at approximately 1V below the common-mode input voltage. For G = 100 RG = 511Ω // 2(22.1kΩ) effective RG = 505Ω OPA602 FIGURE 13. Shield Driver Circuit. +5V Channel 1 VIN + – MPC800 MUX Channel 8 VIN INA111 RG + – ADS574 12 Bits Out Ref FIGURE 14. Multiplexed-Input Data Acquisition System. ® 11 INA111