Precision, Low Power INSTRUMENTATION AMPLIFIERS

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1 INA9 INA9 INA9 Precision, Low Power INSTRUMENTATION AMPLIFIERS FEATURES LOW OFFSET VOLTAGE: µv max LOW DRIFT:.µV/ C max LOW INPUT BIAS CURRENT: na max HIGH CMR: db min INPUTS PROTECTED TO ±V WIDE SUPPLY RANGE: ±. to ±8V LOW QUIESCENT CURRENT: 7µA 8-PIN PLASTIC DIP, SO-8 APPLICATIONS BRIDGE AMPLIFIER THERMOCOUPLE AMPLIFIER RTD SENSOR AMPLIFIER MEDICAL INSTRUMENTATION DATA ACQUISITION DESCRIPTION The and INA9 are low power, general purpose instrumentation amplifiers offering excellent accuracy. Their versatile -op amp design and small size make them ideal for a wide range of applications. Current-feedback input circuitry provides wide bandwidth even at high gain (khz at G = ). A single external resistor sets any gain from to,. provides an industry standard gain equation; INA9 s gain equation is compatible with the AD. The /INA9 is laser trimmed for very low offset voltage (µv), drift (.µv/ C) and high common-mode rejection (db at G ). It operates with power supplies as low as ±.V, and quiescent current is only 7µA ideal for battery operated systems. Internal input protection can withstand up to ±V without damage. The /INA9 is available in 8-pin plastic DIP, and SO-8 surface-mount packages, specified for the C to 8 C temperature range. The is also available in dual configuration, the INA8. V Over-Voltage Protection A kω () 7 kω, INA9 kω : G = kω INA9: G = 9.kΩ A 8 kω () Over-Voltage Protection A kω kω NOTE: () INA9:.7kΩ V International Airport Industrial Park Mailing Address: PO Box, Tucson, AZ 87 Street Address: 7 S. Tucson Blvd., Tucson, AZ 87 Tel: () 7- Twx: 9-9- Internet: FAXLine: (8) 8- (US/Canada Only) Cable: BBRCORP Telex: -9 FAX: () 889- Immediate Product Info: (8) 8-99 Burr-Brown Corporation PDS-9C Printed in U.S.A. October, 99

2 SPECIFICATIONS At T A = C, V S = ±V, R L = kω, unless otherwise noted. P, U PA, UA INA9P, U INA9PA, UA PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS INPUT Offset Voltage, RTI Initial T A = C ± ±/G ± ±/G ± ±/G ± ±/G µv vs Temperature T A = T MIN to T MAX ±. ± /G ±. ± /G ±. ± /G ± ± /G µv/ C vs Power Supply V S = ±.V to ±8V ±. ±/G ± ±/G ± ±/G µv/v Long-Term Stability ±. ±/G µv/mo Impedance, Differential Ω pf Common-Mode 9 Ω pf Common-Mode Voltage Range () = V (V) (V). V (V) (V).7 V Safe Input Voltage ± V Common-Mode Rejection V CM = ±V, R S = kω G= db G= 9 db G= db G= db BIAS CURRENT ± ± ± na vs Temperature ± pa/ C Offset Current ± ± ± na vs Temperature ± pa/ C NOISE VOLTAGE, RTI G =, R S = Ω f = Hz nv/ Hz f = Hz 8 nv/ Hz f = khz 8 nv/ Hz f B =.Hz to Hz. µvp-p Noise Current f=hz.9 pa/ Hz f=khz. pa/ Hz f B =.Hz to Hz pap-p GAIN Gain Equation, (kω/ ) V/V INA9 (9.kΩ/ ) V/V Range of Gain V/V Gain Error G= ±. ±. ±. % G= ±. ±. ±. % G= ±. ±. ±.7 % G= ±. ± ± % Gain vs Temperature () G= ± ± ppm/ C kω (or 9.kΩ) Resistance (, ) ± ± ppm/ C Nonlinearity = ±.V, G= ±. ±. ±. % of FSR G= ±. ±. ±. % of FSR G= ±. ±. ±. % of FSR G= ±. (Note ) % of FSR OUTPUT Voltage: Positive R L = kω (V). (V).9 V Negative R L = kω (V). (V).8 V Load Capacitance Stability pf Short-Circuit Current / ma FREQUENCY RESPONSE Bandwidth, db G=. MHz G= 7 khz G= khz G= khz Slew Rate = ±V, G= V/µs Settling Time,.% G= 7 µs G= 7 µs G= 9 µs G= 8 µs Overload Recovery % Overdrive µs POWER SUPPLY Voltage Range ±. ± ±8 V Current, Total = V ±7 ±7 µa TEMPERATURE RANGE Specification 8 C Operating C θ JA 8-Pin Dip 8 C/W SO-8 SOIC C/W Specification same as P, U or INA9P, U. NOTE: () Input common-mode range varies with output voltage see typical curves. () Guaranteed by wafer test. () Temperature coefficient of the kω (or 9.kΩ) term in the gain equation. () Nonlinearity measurements in G = are dominated by noise. Typical nonlinearity is ±.%.

3 PIN CONFIGURATION 8-Pin DIP and SO-8 V IN V IN V Top View ABSOLUTE MAXIMUM RATINGS V Supply Voltage... ±8V Analog Input Voltage Range... ±V Output Short-Circuit (to ground)... Continuous Operating Temperature... C to C Storage Temperature... C to C Junction Temperature... C Lead Temperature (soldering, s)... C 8 7 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. ORDERING INFORMATION PACKAGE DRAWING TEMPERATURE PRODUCT PACKAGE NUMBER () RANGE PA 8-Pin Plastic DIP C to 8 C P 8-Pin Plastic DIP C to 8 C UA SO-8 Surface-Mount 8 C to 8 C U SO-8 Surface-Mount 8 C to 8 C INA9PA 8-Pin Plastic DIP C to 8 C INA9P 8-Pin Plastic DIP C to 8 C INA9UA SO-8 Surface-Mount 8 C to 8 C INA9U SO-8 Surface-Mount 8 C to 8 C NOTE: () For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. 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.

4 TYPICAL PERFORMANCE CURVES At T A = C, V S = ±V, unless otherwise noted. Gain (db) G = V/V G = V/V G = V/V G = V/V GAIN vs FREQUENCY Common-Mode Rejection (db) 8 COMMON-MODE REJECTION vs FREQUENCY G = V/V G = V/V G = V/V G = V/V k k k M M k k k M Power Supply Rejection (db) 8 POSITIVE POWER SUPPLY REJECTION vs FREQUENCY G = V/V G = V/V G = V/V G = V/V Power Supply Rejection (db) 8 NEGATIVE POWER SUPPLY REJECTION vs FREQUENCY G = V/V G = V/V G = V/V G = V/V k k k M k k k M Common-Mode Voltage (V) INPUT COMMON-MODE RANGE vs OUTPUT VOLTAGE, V S = ±V G G G = G = V V D/ V O V D/ V CM V Output Voltage (V) Common-Mode Voltage (V) INPUT COMMON-MODE RANGE vs OUTPUT VOLTAGE, V S = ±, ±.V G G G = G = V S = ±V V S = ±.V G G = Output Voltage (V)

5 TYPICAL PERFORMANCE CURVES (CONT) At T A = C, V S = ±V, unless otherwise noted. Input-erred Voltage Noise (nv/ Hz) k INPUT- REFERRED NOISE vs FREQUENCY k G = V/V G = V/V G =, V/V Current Noise. k Input Bias Current Noise (pa/ Hz) Settling Time (µs) SETTLING TIME vs GAIN.%.% Gain (V/V) Quiescent Current (µa) QUIESCENT CURRENT and SLEW RATE vs TEMPERATURE. 7 7 I Q Temperature ( C) Slew Rate Slew Rate (V/µs) Input Current (ma) INPUT OVER-VOLTAGE V/I CHARACTERISTICS Flat region represents normal linear operation. G = V/V G = V/V G = V/V V G = V/V I IN V Input Voltage (V) Offset Voltage Change (µv) INPUT OFFSET VOLTAGE WARM-UP 8 8 Time (µs) Input Bias Current (na) INPUT BIAS CURRENT vs TEMPERATURE Typical I B and I OS Range ±na at C 7 7 Temperature ( C) I B I OS

6 TYPICAL PERFORMANCE CURVES (CONT) At T A = C, V S = ±V, unless otherwise noted. (V) OUTPUT VOLTAGE SWING vs OUTPUT CURRENT V OUTPUT VOLTAGE SWING vs POWER SUPPLY VOLTAGE Output Voltage (V) (V). (V).8 (V). (V). (V).8 (V). Output Voltage Swing (V) (V). (V).8 (V). (V). (V).8 (V). R L = kω 8 C C C C 8 C C C 8 C V Output Current (ma) V Power Supply Voltage (V) Short Circuit Current (ma) SHORT-CIRCUIT OUTPUT CURRENT vs TEMPERATURE 8 I SC 8 I SC 7 7 Temperature ( C) Peak-to-Peak Output Voltage (Vpp) MAXIMUM OUTPUT VOLTAGE vs FREQUENCY G =, G = G = k k k M TOTAL HARMONIC DISTORTION NOISE vs FREQUENCY = Vrms khz Measurement Bandwidth G = R L = kω THD N (%).. G =, R L = kω Dashed Portion is noise limited. G =, R L = kω. k k G = V/V R L = kω k

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

8 APPLICATION INFORMATION Figure shows the basic connections required for operation of the /INA9. 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 8Ω in series with the pin will cause a typical device to degrade to approximately 8dB CMR (G = ). SETTING THE GAIN Gain is set by connecting a single external resistor,, connected between pins and 8: : () G = kω INA9: () G = 9.kΩ Commonly used gains and resistor values are shown in Figure. The kω term in Equation (9.kΩ in Equation ) comes from the sum of the two internal feedback resistors of A and A. These on-chip metal film resistors are laser trimmed to accurate absolute values. The accuracy and temperature coefficient of these internal resistors are included in the gain accuracy and drift specifications of the /INA9. 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. DYNAMIC PERFORMANCE The typical performance curve Gain vs Frequency shows that, despite its low quiescent current, the /INA9 achieves wide bandwidth, even at high gain. This is due to the current-feedback topology of the input stage circuitry. Settling time also remains excellent at high gain. NOISE PERFORMANCE The /INA9 provides very low noise in most applications. Low frequency noise is approximately.µvp-p measured from. to Hz (G ). This provides dramatically improved noise when compared to state-of-theart chopper-stabilized amplifiers. V.µF : kω G = DESIRED NEAREST NEAREST GAIN (V/V) (Ω) % (Ω) (Ω) % (Ω) NC NC NC NC.k 9.9k 9.k 9.9k.k.k.k.k.k.k 89.9k.k.k.k.k.k 8 k NC: No Connection. INA9: G = 9.kΩ INA9 8 Over-Voltage Protection Over-Voltage Protection A A Also drawn in simplified form: kω () kω () NOTE: () INA9:.7kΩ 7 kω kω V, INA9.µF kω A kω = G ( ) Load FIGURE. Basic Connections.

9 OFFSET TRIMMING The /INA9 is laser trimmed for low offset voltage and offset voltage 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 with the output. The op amp buffer provides low impedance at the terminal to preserve good common-mode rejection. Microphone, Hydrophone etc. 7kΩ 7kΩ V Thermocouple µa / REF kω OPA77 ±mv Adjustment Range kω Ω Ω V µa / REF Center-tap provides bias current return. FIGURE. Optional Trimming of Output Offset Voltage. INPUT BIAS CURRENT RETURN PATH The input impedance of the /INA9 is extremely high approximately Ω. However, a path must be provided for the input bias current of both inputs. This input bias current is approximately ±na. 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 for proper operation. Figure shows various provisions for an input bias current path. Without a bias current path, the inputs will float to a potential which exceeds the commonmode range, 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 ). With higher source impedance, using two equal resistors provides a balanced input with possible advantages of lower input offset voltage due to bias current and better high-frequency common-mode rejection. INPUT COMMON-MODE RANGE The linear input voltage range of the input circuitry of the /INA9 is from approximately.v below the positive supply voltage to.7v above the negative supply. As a differential input voltage causes the output voltage increase, however, the linear input range will be limited by the output voltage swing of amplifiers A and A. So the FIGURE. Providing an Input Common-Mode Current Path. linear common-mode input range is related to the output voltage of the complete amplifier. This behavior also depends on supply voltage see performance curves Input Common-Mode Range vs Output Voltage. Input-overload can produce an output voltage that appears normal. For example, if an input overload condition drives both input amplifiers to their positive output swing limit, the difference voltage measured by the output amplifier will be near zero. The output of A will be near V even though both inputs are overloaded. LOW VOLTAGE OPERATION The /INA9 can be operated on power supplies as low as ±.V. Performance remains excellent with power supplies ranging from ±.V to ±8V. Most parameters vary only slightly throughout this supply voltage range see typical performance curves. Operation at very low supply voltage requires careful attention to assure that the input voltages remain within their linear range. Voltage swing requirements of internal nodes limit the input commonmode range with low power supply voltage. Typical performance curves, Input Common-Mode Range vs Output Voltage show the range of linear operation for ±V, ±V, and ±.V supplies.

10 =.kω.8kω G = RA LA /.8kΩ RL 9kΩ 9kΩ / OPA kω V G / OPA V G NOTE: Due to the s current-feedback topology, V G is approximately.7v less than the common-mode input voltage. This DC offset in this guard potential is satisfactory for many guarding applications. FIGURE. ECG Amplifier With Right-Leg Drive. V.V V.V REF V R R Ω.V V Pt Cu K Cu FIGURE. Bridge Amplifier. R Ω = Pt at C R C MΩ.µF OPA f db = πr C =.9Hz SEEBECK ISA COEFFICIENT TYPE MATERIAL (µv/ C) R, R E Chromel 8..kΩ Constantan J Iron. 7.8kΩ Constantan K Chromel kΩ Alumel T Copper 8. kω Constantan FIGURE 7. Thermocouple Amplifier With RTD Cold- Junction Compensation. FIGURE. AC-Coupled Instrumentation Amplifier. R I B I O = R G A I O A I B Error Load OPA77 OPA OPA OPA8 ±.na ±pa ±pa ±7fA FIGURE 8. Differential Voltage to Current Converter.

Precision, Low Power INSTRUMENTATION AMPLIFIER

Precision, Low Power INSTRUMENTATION AMPLIFIER FEATURES LOW OFFSET VOLTAGE: µv max LOW DRIFT:.µV/ C max LOW INPUT BIAS CURRENT: na max HIGH CMR: db min INPUTS PROTECTED TO ±V WIDE SUPPLY RANGE: ±. to ±V