Precision OPERATIONAL AMPLIFIER

Transcription

1 OPA77 OPA77 OPA77 Precision OPERATIONAL AMPLIFIER FEATURES LOW OFFSET VOLTAGE: µv max LOW DRIFT:.µV/ C HIGH OPEN-LOOP GAIN: db min LOW QUIESCENT CURRENT:.mA typ REPLACES INDUSTRY-STANDARD OP AMPS: OP-7, OP-77, OP-77, AD77, ETC. DESCRIPTION APPLICATIONS PRECISION INSTRUMENTATION DATA ACQUISITION TEST EQUIPMENT BRIDGE AMPLIFIER THERMOCOUPLE AMPLIFIER The OPA77 precision bipolar op amp feature very low offset voltage and drift. Laser-trimmed offset, drift and input bias current virtually eliminate the need for costly external trimming. The high performance and low cost make them ideally suited to a wide range of precision instrumentation. The low quiescent current of the OPA77 dramatically reduce warm-up drift and errors due to thermoelectric effects in input interconnections. It provides an effective alternative to chopper-stabilized amplifiers. The low noise of the OPA77 maintains accuracy. OPA77 performance gradeouts are available. Packaging options include -pin plastic DIP and SO- surface-mount packages. V+ 7 Trim kω Trim +In Ω Ω Ω V O 6 In Ω µa V International Airport Industrial Park Mailing Address: PO Box, Tucson, AZ 7 Street Address: 67 S. Tucson Blvd., Tucson, AZ 76 Tel: () 76- Twx: 9-9- Internet: FAXLine: () -6 (US/Canada Only) Cable: BBRCORP Telex: FAX: () 9- Immediate Product Info: () Burr-Brown Corporation PDS-E Printed in U.S.A. August, 997

2 OPA77 SPECIFICATIONS At V S = ±V, T A = + C, unless otherwise noted. OPA77F OPA77G PARAMETER CONDITION MIN TYP MAX MIN TYP MAX UNITS OFFSET VOLTAGE Input Offset Voltage 6 µv Long-Term Input Offset ().. µv/mo Voltage Stability Offset Adjustment Range R P = kω ± mv Power Supply Rejection Ratio V S = ±V to ±V db INPUT BIAS CURRENT Input Offset Current... na Input Bias Current. ± ±. na NOISE Input Noise Voltage Hz to Hz () nvrms Input Noise Current Hz to Hz. parms INPUT IMPEDANCE Input Resistance Differential Mode () 6. MΩ Common-Mode GΩ INPUT VOLTAGE RANGE Common-Mode Input Range () ± ± V Common-Mode Rejection V CM = ±V db OPEN-LOOP GAIN R L kω Large Signal Voltage Gain V O = ±V (), 6 V/mV OUTPUT Output Voltage Swing R L kω ±. ± V R L kω ±. ± V R L kω ± ±. V Open-Loop Output Resistance 6 Ω FREQUENCY RESPONSE Slew Rate R L kω.. V/µs Closed-Loop Bandwidth G = +..6 MHz POWER SUPPLY Power Consumption V S = ±V, No Load 6 mw V S = ±V, No Load.. mw Supply Current V S = ±V, No Load. ma At V S = ±V, C T A + C, unless otherwise noted. OFFSET VOLTAGE Input Offset Voltage µv Average Input Offset...7. µv/ C Voltage Drift Power Supply Rejection Ratio V S = ±V to ±V 6 db INPUT BIAS CURRENT Input Offset Current... na Average Input Offset Current. pa/ C Drift (6) Input Bias Current. ± ±6 na Average Input Bias Current 6 pa/ C Drift (6) INPUT VOLTAGE RANGE Common-Mode Input Range ± ±. V Common-Mode Rejection V CM = ±V db OPEN-LOOP GAIN Large Signal Voltage Gain R L kω, V O = ±V 6 V/mV OUTPUT Output Voltage Swing R L kω ± ± V POWER SUPPLY Power Consumption V S = ±V, No Load 6 7 mw Supply Current V S = ±V, No Load ma Same as specification for product to left. NOTES: () Long-Term Input Offset Voltage Stability refers to the averaged trend line of V OS vs time over extended periods after the first days of operation. Excluding the initial hour of operation, changes in V OS during the first operating days are typically less than µv. () Sample tested. () Guaranteed by design. () Guaranteed by CMRR test condition. () To insure high open-loop gain throughout the ±V output range, A OL is tested at V V O V, V V O +V, and V V O +V. (6) Guaranteed by end-point limits. OPA77

3 PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS Top View Offset Trim In +In V 7 6 DIP/SOIC Offset Trim V+ VO No Internal Connection Power Supply Voltage... ±V Differential Input Voltage... ±V Input Voltage... ±V S Output Short Circuit... Continuous Operating Temperature: Plastic DIP (P), SO- (S)... C to + C θ JA (PDIP)... C/W θ JA (SOIC)... 6 C/W Storage Temperature: Plastic DIP (P), SO- (S)... 6 C to + C Junction Temperature... + C Lead Temperature (soldering, s) P packages... + C (soldering, s) S package C PACKAGE/ORDERING INFORMATION PACKAGE DRAWING TEMPERATURE PRODUCT PACKAGE NUMBER () RANGE OPA77FP -Pin Plastic DIP 6 C to + C OPA77GP -Pin Plastic DIP 6 C to + C OPA77GS SO- Surface-Mount C to + C NOTE: () For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. ELECTROSTATIC DISCHARGE SENSITIVITY Any integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. ESD can cause damage ranging 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 published specifications. Burr-Brown s standard ESD test method consists of five V positive and negative discharges (pf in series with.kω) applied to each pin. Failure to observe proper handling procedures could result in small changes to the OPA77 s input bias current. 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. OPA77

4 TYPICAL PERFORMANCE CURVES At T A = + C, V S = ±V, unless otherwise noted. TOTAL HARMONIC DISTORTION AND NOISE vs FREQUENCY 7. MAXIMUM V OUT vs I OUT (Negative Swing) A = db, Vrms, kω load V S = ±V THD + N (%).. Noninverting Inverting V OUT (V). 7. V S = ±V V S = ±V khz low pass filtered. k k k. V S = ±V 6 I OUT (ma) 7. MAXIMUM V OUT vs I OUT (Positive Swing) WARM-UP OFFSET VOLTAGE DRIFT V OUT (V) V S = ±V. V S = ±V V 7. S = ±V. V S = ±V 6 6 I OUT (ma) Offset Voltage Change (µv) Time from Power Supply Turn-On (s) OFFSET VOLTAGE CHANGE DUE TO THERMAL SHOCK Device Immersed in 7 C Inert Liquid CLOSED-LOOP RESPONSE vs FREQUENCY Absolute Change in Input Offset Voltage (µv) Plastic DIP Closed-Loop Gain (db) Time (s) k k k M M OPA77

5 TYPICAL PERFORMANCE CURVES (CONT) At T A = + C, V S = ±V, unless otherwise noted. 6 OPEN-LOOP GAIN/PHASE vs FREQUENCY CMRR vs FREQUENCY Gain Open-Loop Gain (db) 6 Phase 9 Phase Shift (Degrees) CMRR (db) 9.. k k k M k k k Power Supply Rejection (db) 9 7. POWER SUPPLY REJECTION vs FREQUENCY k k Input Bias and Input Offset Current (na) INPUT BIAS AND INPUT OFFSET CURRENT vs TEMPERATURE I B I OS 6 Temperature ( C) RMS Noise (µv). TOTAL NOISE vs BANDWIDTH (.Hz to Frequency Indicated) Input Noise Voltage (nv/ Hz) k INPUT NOISE VOLTAGE DENSITY vs FREQUENCY R = S R S = R S = kω Thermal noise of source resistors included.. k k k Bandwidth (Hz) k k OPA77

6 TYPICAL PERFORMANCE CURVES (CONT) At T A = + C, V S = ±V, unless otherwise noted. MAXIMUM OUTPUT SWING vs FREQUENCY POWER CONSUMPTION vs POWER SUPPLY Peak-to-Peak Amplitude (V) 6 G = + R L = kω Power Consumption (mw) k k k M Total Supply Voltage (V) MAXIMUM OUTPUT VOLTAGE vs LOAD RESISTANCE OUTPUT SHORT-CIRCUIT CURRENT vs TIME Maximum Output (V) Positive Output Negative Output Output Short-Circuit Current (ma) I SC I SC+ k k Load Resistance to Ground ( Ω) Time from Output Being Shorted (min) OPA77 6

7 APPLICATIONS INFORMATION The OPA77 is unity-gain stable, making it easy to use and free from oscillations in the widest range of circuitry. Applications with noisy or high impedance power supply lines may require decoupling capacitors close to the device pins. In most cases.µf ceramic capacitors are adequate. The OPA77 has very low offset voltage and drift. To achieve highest performance, circuit layout and mechanical conditions must be optimized. Offset voltage and drift can be degraded by small thermoelectric potentials at the op amp inputs. Connections of dissimilar metals will generate thermal potential which can mask the ultimate performance of the OPA77. These thermal potentials can be made to cancel by assuring that they are equal in both input terminals.. Keep connections made to the two input terminals close together.. Locate heat sources as far as possible from the critical input circuitry.. Shield the op amp and input circuitry from air currents such as cooling fans. OFFSET VOLTAGE ADJUSTMENT The OPA77 has been laser-trimmed for low offset voltage and drift so most circuits will not require external adjustment. Figure shows the optional connection of an external potentiometer to adjust offset voltage. This adjustment should not be used to compensate for offsets created elsewhere in a system since this can introduce excessive temperature drift. INPUT PROTECTION The inputs of the OPA77 are protected with Ω series input resistors and diode clamps as shown in the simplified circuit diagram. The inputs can withstand ±V differential inputs without damage. The protection diodes will, of course, conduct current when the inputs are overdriven. This may disturb the slewing behavior of unity-gain follower applications, but will not damage the op amp. V IN FIGURE. Optional Offset Nulling Circuit. OPA77 Trim Range is approximately ±.mv VOUT NOISE PERFORMANCE The noise performance of the OPA77 is optimized for circuit impedances in the range of kω to kω. Total noise in an application is a combination of the op amp s input voltage noise and input bias current noise reacting with circuit impedances. For applications with higher source impedance, the OPA67 FET-input op amp will generally provide lower noise. For very low impedance applications, the OPA7 will provide lower noise. INPUT BIAS CURRENT CANCELLATION The input stage base current of the OPA77 is internally compensated with an equal and opposite cancellation current. The resulting input bias current is the difference between the input stage base current and the cancellation current. This residual input bias current can be positive or negative. When the bias current is cancelled in this manner, the input bias current and input offset current are approximately the same magnitude. As a result, it is not necessary to balance the DC resistance seen at the two input terminals (Figure ). A resistor added to balance the input resistances may actually increase offset and noise. V+ kω R R R Op Amp R OPA77 R B = R R No bias current cancellation resistor needed (a) (b) Conventional op amp with external bias current cancellation resistor. OPA77 with no external bias current cancellation resistor. FIGURE. Input Bias Current Cancellation. 7 OPA77