Datasheet OP177 (Analog Devices) - 10

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OP177 Data Sheet PRECISION HIGH GAIN DIFFERENTIAL AMPLIFIER ISOLATING LARGE CAPACITIVE LOADS
The high gain, gain linearity, CMRR, and low TCVOS of the The circuit shown in Figure 29 reduces maximum slew rate but OP177 make it possible to obtain performance not previously allows driving capacitive loads of any size without instability. available in single stage, very high gain amplifier applications. Because the 100 Ω resistor is inside the feedback loop, the effect See Figure 28. on output impedance is reduced to insignificance by the high R1 R3 open loop gain of the OP177. For best CMR, must equal R2 R4
RF 10pF
In this example, with a 10 mV differential signal, the maximum errors are listed in Table 6.
+15V R2 0.1µF 1MΩ R +15V S 2 INPUT – 7 6 100Ω 0.1µF OP177 OUTPUT 3 R + C 1 4 LOAD 0.1µF 1kΩ 7 2 – R 6
028
3 OP177
89-
1kΩ 3 –15V
002
+ 4
Figure 29. Isolating Capacitive Loads
R4 0.1µF 1MΩ BILATERAL CURRENT SOURCE
-027
–15V
289 00 The current sources shown in Figure 30 supply both positive Figure 28. Precision High Gain Differential Amplifier and negative currents into a grounded load.
Table 6. High Gain Differential Amplifier Performance
Note that
Type Amount
 R4  Common-Mode Voltage 0.1%/V R  5  1  R2  Gain Linearity, Worst Case 0.02% Z  O R5  R4 R3 TCV  OS 0.0003%/°C TCI R2 R1 OS 0.008%/°C and that for ZO to be infinite R5  R4 R3 must  R2 R1
PRECISION ABSOLUTE VALUE AMPLIFIER
The high gain and low TCVOS assure accurate operation with inputs from microvolts to volts. In this circuit, the signal always appears as a common-mode signal to the operational amplifiers (for details, see Figure 31).
BASIC CURRENT SOURCE 100mA CURRENT SOURCE R3 1kΩ R3 +15V R1 100kΩ 2 R1 2 V – V – 2N2222 IN IN R 6 6 50Ω 2 OP177 OP177 100kΩ 3 R2 3 + + R 2N2907 5 R5 R 10Ω 4 990Ω R4 –15V IOUT ≤ 15mA IOUT ≤ 100mA R I 3 OUT = VIN R
-029
1 × R5
289
GIVEN R3 = R4 + R5, R1 = R2
00 Figure 30. Bilateral Current Source Rev. H | Page 10 of 16 Document Outline FEATURES PIN CONFIGURATION GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM REVISION HISTORY SPECIFICATIONS ELECTRICAL CHARACTERISTICS TEST CIRCUITS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION TYPICAL PERFORMANCE CHARACTERISTICS APPLICATIONS INFORMATION GAIN LINEARITY THERMOCOUPLE AMPLIFIER WITH COLD-JUNCTION COMPENSATION PRECISION HIGH GAIN DIFFERENTIAL AMPLIFIER ISOLATING LARGE CAPACITIVE LOADS BILATERAL CURRENT SOURCE PRECISION ABSOLUTE VALUE AMPLIFIER PRECISION POSITIVE PEAK DETECTOR PRECISION THRESHOLD DETECTOR/AMPLIFIER OUTLINE DIMENSIONS ORDERING GUIDE