Precision Gain = 10 DIFFERENTIAL AMPLIFIER

Transcription

1 Precision Gain = DIFFERENTIAL AMPLIFIER FEATURES ACCURATE GAIN: ±.% max HIGH COMMON-MODE REJECTION: 8dB min NONLINEARITY:.% max EASY TO USE PLASTIC 8-PIN DIP, SO-8 SOIC PACKAGES APPLICATIONS G = DIFFERENTIAL AMPLIFIER G = + AMPLIFIER G = AMPLIFIER G = + AMPLIFIER INSTRUMENTATION AMPLIFIER DESCRIPTION The is a monolithic Gain = differential amplifier consisting of a precision op amp and on-chip metal film resistors. The resistors are laser trimmed for accurate gain and high common-mode rejection. Excellent TCR tracking of the resistors maintains gain accuracy and common-mode rejection over temperature. In R kω R 7 Sense Output The differential amplifier is the foundation of many commonly used circuits. The provides this precision circuit function without using an expensive resistor network. The is available in 8-pin plastic DIP and SO-8 surface-mount packages. +In R kω 4 Reference International Airport Industrial Park Mailing Address: PO Box 4, Tucson, AZ 874 Street Address: 7 S. Tucson Blvd., Tucson, AZ 87 Tel: () 74- Twx: 9-9- Internet: FAXLine: (8) 48- (US/Canada Only) Cable: BBRCORP Telex: -49 FAX: () 889- Immediate Product Info: (8) Burr-Brown Corporation PDS-79F Printed in U.S.A. August, 998 SBOS

2 SPECIFICATIONS ELECTRICAL At + C, V S = ±V, unless otherwise specified. KP, U PARAMETER CONDITIONS MIN TYP MAX UNITS GAIN Initial () V/V Error.. % vs Temperature 4 ppm/ C Nonlinearity ().. % OUTPUT Related Voltage I O = +ma, ma V Rated Current = V +, ma Impedance. Ω Current Limit To Common +4/ ma Capacitive Load Stable Operation pf INPUT Impedance Differential kω Common-Mode kω Voltage Range Differential ± V Common-Mode ± V Common-Mode Rejection () T A = T MIN to T MAX 8 db OFFSET VOLTAGE RTI (4) Initial µv vs Temperature. µv/ C vs Supply ±V S = V to 8V µv/v vs Time µv/mo NOISE VOLTAGE RTI () f B =.Hz to Hz µvp-p f O = khz nv/ Hz DYNAMIC RESPONSE Small Signal db MHz Full Power BW = Vp-p khz Slew Rate V/µs Settling Time:.% = V Step µs.% = V Step µs.% V CM = V Step, V DIFF = V µs POWER SUPPLY Rated ± V Voltage Range Derated Performance ± ±8 V Quiescent Current = V ±. ± ma TEMPERATURE RANGE Specification +7 C Operation 4 +8 C Storage + C NOTES: () Connected as difference amplifier (see Figure ). () Nonlinearity is the maximum peak deviation from the best-fit straight line as a percent of full-scale peakto-peak output. () With zero source impedance (see Maintaining CMR section). (4) Includes effects of amplifiers s input bias and offset currents. () Includes effect of amplifier s input current noise and thermal noise contribution of resistor network.

3 PIN CONFIGURATION Top View Ref In +In () 8 4 kω kω ABSOLUTE MAXIMUM RATINGS DIP/SOIC Power Supply Voltage... ±8V Input Voltage Range... ±V S Operating Temperature Range: P, U... 4 C to +8 C Storage Temperature Range... 4 C to +8 C Lead Temperature (soldering, s): P... + C Wave Soldering (s, max) U... + C Output Short Circuit to Common... Continuous NC Output Sense NOTE: () Pin indentifier for SO-8 package. Model number identification may be abbreviated on SO-8 package due to limited available space. 7 ELECTROSTATIC DISCHARGE SENSITIVITY This integral 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 published specifications. PACKAGE/ORDERING INFORMATION PACKAGE DRAWING TEMPERATURE PRODUCT PACKAGE NUMBER () RANGE KP 8-Pin Plastic DIP C to +7 C U SO-8 Surface Mount 8 C to +7 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. STEP RESPONSE SMALL SIGNAL RESPONSE (No Load) Output Voltage (mv) µs/div µs/div SMALL SIGNAL RESPONSE (R LOAD =, C LOAD = pf) TOTAL HARMONIC DISTORTION AND NOISE vs FREQUENCY A = db, Vrms, kω load Output Voltage (mv) THD + N (%).. Noninverting Inverting µs/div. khz low-pass filtered k k k Frequency (Hz) UT (V) MAXIMUM UT vs I OUT (Negative Swing) V S = ±8V V S = ±V V S = ±V UT (V) MAXIMUM UT vs I OUT (Positive Swing) V S = ±8V V S = ±V V S = ±V. V S = ±V 4 8 I OUT (ma). V S = ±V 8 4 I OUT (ma) 4

5 TYPICAL PERFORMANCE CURVES (CONT) At T A = + C, V S = ±V, unless otherwise noted. CMR vs FREQUENCY 4 POWER SUPPLY REJECTION vs FREQUENCY CMR (db) 9 8 PSRR (db) 8 7 k k k Frequency (Hz) 4 k k k Frequency (Hz) APPLICATIONS INFORMATION Figure shows the basic connections required for operation of the. Power supply bypass capacitors should be connected close to the device pins as shown. µf 4 7 R R µf kω V Ref terminal will be summed with the output signal. The source impedance of a signal applied to the Ref terminal should be less than Ω to maintain good common-mode rejection. Figure shows a voltage applied to pin to trim the offset voltage of the. The known Ω source impedance of the trim circuit is compensated by the Ω resistor in series with pin to maintain good CMR. V R kω + UT = (V V ) V V Ω R R R FIGURE. Basic Power Supply and Signal Connections. The differential input signal is connected to pins and as shown. The source impedance connected to the inputs must be equal to assure good common-mode rejection. A Ω mismatch in source impedance will degrade the commonmode rejection of a typical device to approximately 8dB. If the source has a known source impedance mismatch, an additional resistor in series with one input can be used to preserve good common-mode rejection. The output is referred to the output reference terminal (pin ) which is normally grounded. A voltage applied to the Compensates for some impedance at pin. See text. = V V Offset Adjustment Range = ±mv FIGURE. Offset Adjustment. Ω 499kΩ +V V Referring to Figure, the CMR depends upon the match of the internal /R ratio to the R /R ratio. A CMR of db requires resistor matching of.%. To maintain high CMR over temperature, the resistor TCR tracking must be better than ppm/ C. These accuracies are difficult and expensive to reliably achieve with discrete components.

6 V Ω kω Ω Gain Adjust E In A R V Ω kω To eliminate adjustment interactions, first adjust gain with V grounded. Ω FIGURE. Difference Amplifier with Gain and CMR Adjust. kω V kω Gain Error =.% maximum Nonlinearity =.% maximum Gain Drift =.ppm/ C FIGURE 4. Precision G = Inverting Amplifier. = V E CMR Adjust E +In R A R E = ( + R /R ) (E E ) To make a high performance high gain instrumentation amplifier, the can be combined with state-of-the-art op amps. For low source impedance applications, OPA7s will give the best noise, offset, and temperature drift. At source impedances above about kω, the bias current noise of the OPA7 reacting with input impedance degrades noise. For these applications, use an OPA or a dual OPA FET input op amp for lower noise. For an electrometer grade IA, use the OPA8 see table below. Using the for the difference amplifier also extends the input commonmode range of the instrumentation amplifier to ±V. A conventional IA with a unity-gain difference amplifier has an input common-mode range limited to ±V for an output swing of ±V. This is because a unity-gain difference amp needs ±V at the input for V at the output, allowing only V additional for common-mode. R R GAIN CMRR NOISE AT khz A, A (Ω) (kω) (V/V) (db) I b (pa) (nv/ Hz) OPA7A OPAB OPA8LM FIGURE. Precision Instrumentation Amplifier. R R kω E Output R R kω V V R kω V V = V + V V IN = V IN FIGURE 7. Precision Summing Amplifier. ±V Safe Input R kω This circuit follows an / divider with a gain of for an overall gain of unity. With an / divider, the input signal can exceed V without damage. FIGURE. Voltage Follower with Input Protection. V IN = V IN Gain Error =.% maximum FIGURE 8. Precision G = Buffer.

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