Precision INSTRUMENTATION AMPLIFIER

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1 Precision INSTRUMENTATION AMPLIFIER FEATURES LOW OFFSET VOLTAGE: 5µV max LOW DRIFT:.5µV/ C max LOW INPUT BIAS CURRENT: na max HIGH COMMON-MODE REJECTION: 5dB min INPUT OVER-VOLTAGE PROTECTION: ±V WIDE SUPPLY RANGE: ±.5 to ±8V LOW QUIESCENT CURRENT: ma max 8-PIN PLASTIC AND SOL- APPLICATIONS BRIDGE AMPLIFIER THERMOCOUPLE AMPLIFIER RTD SENSOR AMPLIFIER MEDICAL INSTRUMENTATION DATA ACQUISITION 7 V DESCRIPTION The is a low cost, general purpose instrumentation amplifier offering excellent accuracy. Its versatile -op amp design and small size make it ideal for a wide range of applications. A single external resistor sets any gain from to,. Internal input protection can withstand up to ±V without damage. The is laser trimmed for very low offset voltage (5µV), drift (.5µV/ C) and high common-mode rejection (5dB at G = ). It operates with power supplies as low as ±.5V, allowing use in battery operated and single 5V supply systems. Quiescent current is ma maximum. The is available in 8-pin plastic and SOL- surface-mount packages. Both are specified for the C to 85 C temperature range. () () () 8 (5) (5) A A A Feedback () () 5 () DIP Connected Internally G = 5kΩ DIP V (7) (SOIC) International Airport Industrial Park Mailing Address: PO Box, Tucson, AZ 857 Street Address: 7 S. Tucson Blvd., Tucson, AZ 857 Tel: (5) 7- Twx: Internet: FAXLine: (8) 58- (US/Canada Only) Cable: BBRCORP Telex: -9 FAX: (5) Immediate Product Info: (8) Burr-Brown Corporation PDS-D Printed in U.S.A. March, 998 SBOS

2 SPECIFICATIONS ELECTRICAL At T A = 5 C, V S = ±5V, R L = kω, unless otherwise noted. BP, BU AP, AU PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS INPUT Offset Voltage, RTI Initial T A = 5 C ± /G ±5 /G ±5 /G ±5 5/G µv vs Temperature T A = T MIN to T MAX ±..5/G ±.5 5/G ±.5 5/G ± /G µv/ C vs Power Supply V S = ±.5V to ±8V.5 /G /G µv/v Long-Term Stability ±..5/G µv/mo Impedance, Differential Ω pf Common-Mode Ω pf Input Common-Mode Range ± ±.5 V Safe Input Voltage ± V Common-Mode Rejection V CM = ±V, R S = kω G = db G = db G = db G = 5 db BIAS CURRENT ±.5 ± ±5 na vs Temperature ±8 pa/ C OFFSET CURRENT ±.5 ± ±5 na vs Temperature ±8 pa/ C NOISE VOLTAGE, RTI G =, R S = Ω f = Hz 5 nv/ Hz f = Hz nv/ Hz f = khz nv/ Hz f B =.Hz to Hz. µvp-p Noise Current f=hz. pa/ Hz f=khz. pa/ Hz f B =.Hz to Hz 8 pap-p GAIN Gain Equation (5kΩ/ ) V/V Range of Gain V/V Gain Error G = ±. ±.5 % G = ±. ±. ±.5 % G = ±.5 ±.5 ±.7 % G = ±.5 ± ± % Gain vs Temperature G = ± ± ± ppm/ C 5kΩ Resistance () ±5 ± ppm/ C Nonlinearity G = ±. ±. ±. % of FSR G = ±.5 ±. ±. % of FSR G = ±.5 ±. ±. % of FSR G = ±. ±. ±. % of FSR OUTPUT Voltage I O = 5mA, T MIN to T MAX ±.5 ±.7 V V S = ±.V, R L = kω ± ±.5 V V S = ±.5V, R L = kω ± ±.5 V Load Capacitance Stability pf Short Circuit Current /5 ma FREQUEY RESPONSE Bandwidth, db G = MHz G = khz G = khz G = khz Slew Rate = ±V, G =.. V/µs Settling Time,.% G = 8 µs G = µs G = µs G = µs Overload Recovery 5% Overdrive µs POWER SUPPLY Voltage Range ±.5 ±5 ±8 V Current = V ±. ± ma TEMPERATURE RANGE Specification 85 C Operating 5 C θ JA 8 C/W Specification same as BP/BU. NOTE: () Temperature coefficient of the 5kΩ 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.

3 PIN CONFIGURATIONS P Package V IN V IN V U Package Top View 8-Pin DIP V SOL- Surface-Mount Top View ELECTROSTATIC DISCHARGE SENSITIVITY 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. V IN V IN V V Feedback PACKAGE/ORDERING INFORMATION PACKAGE DRAWING TEMPERATURE PRODUCT PACKAGE NUMBER () RANGE AP 8-Pin Plastic DIP C to 85 C BP 8-Pin Plastic DIP C to 85 C AU SOL- Surface-Mount C to 85 C BU SOL- Surface-Mount C to 85 C NOTE: () For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. ABSOLUTE MAXIMUM RATINGS () Supply Voltage... ±8V Input Voltage Range... ±V Output Short-Circuit (to ground)... Continuous Operating Temperature... C to 5 C Storage Temperature... C to 5 C Junction Temperature... 5 C Lead Temperature (soldering, s)... C NOTE: () Stresses above these ratings may cause permanent damage.

4 TYPICAL PERFORMAE CURVES At T A = 5 C, V S = ±5V, unless otherwise noted. Gain (V/V) k GAIN vs FREQUEY Common-Mode Rejection (db) 8 COMMON-MODE REJECTION vs FREQUEY G =, k G = G = k G = G = G = k k k M Frequency (Hz) k k k M Frequency (Hz) Common-Mode Voltage (V) INPUT COMMON-MODE VOLTAGE RANGE vs OUTPUT VOLTAGE Limited by A Output Swing V D/ V D/ V CM (Any Gain) A Output Swing Limit Limited by A Output Swing Output Voltage (V) Limited by A Output Swing A Output Swing Limit Limited by A Output Swing Power Supply Rejection (db) 8 POSITIVE POWER SUPPLY REJECTION vs FREQUEY k k k M Frequency (Hz) G = G = G = G = Power Supply Rejection (db) 8 NEGATIVE POWER SUPPLY REJECTION vs FREQUEY G = G = G = k k k M Frequency (Hz) G = Input-erred Noise Voltage (nv/ Hz) k INPUT-REFERRED NOISE VOLTAGE vs FREQUEY G =, k Frequency (Hz) G = G = G = BW Limit k

5 TYPICAL PERFORMAE CURVES (CONT) At T A = 5 C, V S = ±5V, unless otherwise noted. SETTLING TIME vs GAIN OFFSET VOLTAGE WARM-UP vs TIME Settling Time (µs) 8.%.% Offset Voltage Change (µv) G Gain (V/V) Time from Power Supply Turn-on (s) Input Bias and Input Offset Current (na) ±I B INPUT BIAS AND INPUT OFFSET CURRENT vs TEMPERATURE I OS Temperature ( C) Input Bias Current (ma) 5 INPUT BIAS CURRENT vs DIFFERENTIAL INPUT VOLTAGE G = G = G = G = Differential Overload Voltage (V) Input Bias Current (ma) 5 One Input INPUT BIAS CURRENT vs COMMON-MODE INPUT VOLTAGE Normal Operation I b I b Both Inputs One Input Both Inputs Common-Mode Voltage (V) Peak-to-Peak Amplitude (V) 8 8 MAXIMUM OUTPUT SWING vs FREQUEY G =, G = G = k k k M Frequency (Hz) 5

6 TYPICAL PERFORMAE CURVES (CONT) At T A = 5 C, V S = ±5V, unless otherwise noted.. SLEW RATE vs TEMPERATURE OUTPUT CURRENT LIMIT vs TEMPERATURE Slew Rate (V/µs).8... Short Circuit Current (ma) 5 5 I CL I CL Temperature ( C) Temperature ( C).8 QUIESCENT CURRENT vs TEMPERATURE. QUIESCENT CURRENT AND POWER DISSIPATION vs POWER SUPPLY VOLTAGE Quiescent Current (ma).... Quiescent Current (ma) Power Dissipation Quiescent Current 8 Power Dissipation (mw) Temperature ( C) 5. ± ± ±9 ± ±5 ±8 Power Supply Voltage (V) POSITIVE SIGNAL SWING vs TEMPERATUE (R L = kω) V S = ±5V NEGATIVE SIGNAL SWING vs TEMPERATUE (R L = kω) V S = ±5V Output Voltage (V) 8 V S = ±.V V S = ±.5V Output Voltage (V) 8 V S = ±.V V S = ±.5V Temperature ( C) Temperature ( C)

7 TYPICAL PERFORMAE CURVES (CONT) At T A = 5 C, V S = ±5V, unless otherwise noted. LARGE SIGNAL RESPONSE, G = SMALL SIGNAL RESPONSE, G = V mv V mv LARGE SIGNAL RESPONSE, G = SMALL SIGNAL RESPONSE, G = V mv V mv INPUT-REFERRED NOISE,. to Hz.µV/div s/div 7

8 APPLICATION INFORMATION Figure shows the basic connections required for operation of the. 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 () 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 pin will cause a typical device to degrade to approximately 8dB CMR (G = ). SETTING THE GAIN Gain of the is set by connecting a single external resistor, : G = 5 kω () Commonly used gains and resistor values are shown in Figure. The 5kΩ term in equation () comes from the sum of the two internal feedback resistors. These are on-chip metal film resistors which are laser trimmed to accurate absolute val- ues. The accuracy and temperature coefficient of these resistors are included in the gain accuracy and drift specifications of the. The stability and temperature drift of the external gain setting resistor,, also affects gain. s contribution to gain accuracy and drift can be directly inferred from the gain equation (). 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 or greater. NOISE PERFORMAE The provides very low noise in most applications. For differential source impedances less than kω, the INA may provide lower noise. For source impedances greater than 5kΩ, the INA FET-input instrumentation amplifier may provide lower noise. Low frequency noise of the is approximately.µvp-p measured from. to Hz. This is approximately one-tenth the noise of low noise chopper-stabilized amplifiers. V.µF Pin numbers are for DIP packages. 7 A A = G ( ) G = 5kΩ 8 Load A 5.µF DESIRED NEAREST % GAIN (Ω) (Ω) No Connection No Connection 5.k 9.9k 5.5k.k 5.55k 5.k.k.k 5.k.k V Also drawn in simplified form: V IN V IN FIGURE. Basic Connections. 8

9 OFFSET TRIMMING The is laser trimmed for very low offset voltage and drift. Most applications require no external offset adjustment. Figure shows an optional circuit for trimming the output offset voltage. The voltage applied to 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. 7kΩ 7kΩ V µa / REF Thermocouple kω OPA77 ±mv Adjustment Range kω Ω Ω µa / REF FIGURE. Optional Trimming of Output Offset Voltage. INPUT BIAS CURRENT RETURN PATH The input impedance of the is extremely high approximately Ω. However, a path must be provided for the input bias current of both inputs. This input bias current is typically less than ±na (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 circuitry must provide a path for this input bias current if the is to operate properly. Figure 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 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 ). 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 COMMON-MODE RANGE The linear common-mode range of the input op amps of the is approximately ±.75V (or.5v 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, A and A. The commonmode range is related to the output voltage of the complete amplifier see performance curve Input Common-Mode Range vs Output Voltage. V Center-tap provides bias current return. FIGURE. Providing an Input Common-Mode Current Path. A combination of common-mode and differential input signals can cause the output of A or A to saturate. Figure shows the output voltage swing of A and A expressed in terms of a common-mode and differential input voltages. Output swing capability of these internal amplifiers is the same as the output amplifier, A. For applications where input common-mode range must be maximized, limit the output voltage swing by connecting the in a lower gain (see performance curve Input Common-Mode Voltage Range vs Output Voltage ). If necessary, add gain after the to increase the voltage swing. Input-overload often produces an output voltage that appears normal. For example, an input voltage of V on one input and V on the other input will obviously exceed the linear common-mode range of both input amplifiers. Since both input amplifiers are saturated to nearly the same output voltage limit, the difference voltage measured by the output amplifier will be near zero. The output of the will be near V even though both inputs are overloaded. INPUT PROTECTION The inputs of the are individually protected for voltages up to ±V. For example, a condition of V on one input and V 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.5ma). The typical performance curve Input Bias Current vs Common-Mode Input Voltage shows this input 9

10 current limit behavior. The inputs are protected even if no power supply voltage is present. OUTPUT VOLTAGE SENSE (SOL- package only) The surface-mount version of the has a separate output sense feedback connection (pin ). Pin must be connected to the output terminal (pin ) for proper operation. (This connection is made internally on the DIP version of the.) The output sense connection can be used to sense the output voltage directly at the load for best accuracy. Figure 5 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 C. Heavy loads or long lines can be driven by connecting a buffer inside the feedback path (Figure ). V CM G V D V V D A G = 5kΩ A = G V D V D V CM A V CM G V D V FIGURE. Voltage Swing of A and A. Surface-mount package version only. Surface-mount package version only. Output Sense C pf Load Output Sense 8Ω OPA R L I L : ±ma Equal resistance here preserves good common-mode rejection. FIGURE 5. Remote Load and Ground Sensing. FIGURE. Buffered Output for Heavy Loads. Shield is driven at the common-mode potential. Ω OPA.kΩ.kΩ 5Ω For G = = 5Ω // (.kω) effective = 55Ω FIGURE 7. Shield Driver Circuit.

11 V V Equal line resistance here creates a small common-mode voltage which is rejected by. REF µa RTD R Z Resistance in this line causes a small common-mode voltage which is rejected by. = V at R RTD = R Z FIGURE 8. RTD Temperature Measurement Circuit. V.V REF R 7k Ω R 8.k Ω K N8 () Cu Cu R 5.k Ω () R7 MΩ R Ω R5 5Ω R Ω Zero Adj SEEBECK ISA COEFFICIENT R R TYPE MATERIAL (µv/ C) (R = Ω) (R 5 R = Ω) E Chromel kΩ 5.kΩ Constantan J Iron 5..kΩ.9kΩ Constantan K Chromel 9. 5.kΩ 8.kΩ Alumel T Copper kΩ 8.5kΩ Constantan NOTES: ().mv/ C at µa. () R 7 provides down-scale burn-out indication. FIGURE 9. Thermocouple Amplifier With Cold Junction Compensation.

12 .8kΩ RA LA /.8kΩ G = RL 9kΩ 9kΩ / OPA kω / OPA FIGURE. ECG Amplifier With Right-Leg Drive. V R Bridge G = 5 C.µF MΩ Ω OPA f db = πr C =.59Hz FIGURE. Bridge Transducer Amplifier. FIGURE. AC-Coupled Instrumentation Amplifier. R I B I O = R G A Load I O A OPA77 OPA OPA8 I B Error ±.5nA pa 75fA FIGURE. Differential Voltage-to-Current Converter.

13 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. Customers are responsible for their applications using TI components. In order to minimize risks associated with the customer s applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. TI s publication of information regarding any third party s products or services does not constitute TI s approval, warranty or endorsement thereof. Copyright, Texas Instruments Incorporated

Precision G = 100 INSTRUMENTATION AMPLIFIER

Precision G = 100 INSTRUMENTATION AMPLIFIER Precision G = INSTRUMENTATION AMPLIFIER FEATURES LOW OFFSET VOLTAGE: 5µV max LOW DRIFT:.5µV/ C max LOW INPUT BIAS CURRENT: na max HIGH COMMON-MODE REJECTION: db min INPUT OVERVOLTAGE PROTECTION: ±V WIDE