AD746A HIGH SPEED 3 OR AMP INSTRUMENTATIONTable I. Performance Summary for the 3 Op AmpAMPLIFIER CIRCUITInstrumentation Amplifier Circuit The instrumentation amplifier circuit shown in Figure 23 can T provide a range of gains from 2 up to 1000 and higher. The SETTLEGainR circuit bandwidth is 2.5 MHz at a gain of 2 and 750 kHz at a GBandwidth(0.01%) gain of 10; settling time for the entire circuit is less than 2 µs to 2 20 kΩ 2.5 MHz 1.0 µs within 0.01% for a 10 volt step, (G = 10). 10 4.04 kΩ 1 MHz 2.0 µs 100 404 Ω 290 kHz 5.0 µs Figure 25. Settling Time of the 3 Op Amp Instrumentation Amplifier. Gain = 10, Horizontal Scale: 0.5 µs/Div, Vertical Scale: 5 V/Div. Error Signal Scale: 0.01%/Div. THD Performance Considerations The AD746 was carefully optimized to offer excellent performance in terms of total harmonic distortion (THD) in signal processing applications. The THD level when operating the AD746 in inverting gain applications will show a gradual rise from the distortion floor of 20 dB/decade (see Figure 28). In noninverting applications, care should be taken to balance the source impedances at both the inverting and noninverting inputs, to avoid distortion caused by the modulation of input Figure 23. A High Performance, 3 Op Amp, Instrumenta- capacitance inherent in all BiFET op amps. tion Amplifier Circuit Figure 26. THD Measurement, Inverter Circuit Figure 24. Pulse Response of the 3 Op Amp Instrumentation Amplifier. Gain = 10, Horizontal Scale: 0.5 µs/Div, Vertical Scale: 5 V/Div. Figure 27. THD Measurement, Follower Circuit REV. B –7–