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AC Negative Feedback OpAmp Circuits
14 questions By Tony R. Kuphaldt
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Question 13 of 14
Calculate the impedance (in complex number form) “seen” by the AC signal source as it drives the passive integrator circuit on the left, and the active integrator circuit on the right. In both cases, assume that nothing is connected to the Vout terminal:
Reveal answer
Notes:The most important thing to be learned here is that the opamp “isolates” the signal source from whatever impedance is in the feedback loop, so that the input impedance (in this case, the 10 kΩ resistor) is the only impedance “visible” to that source. This has profound effects on the phase relationship between the output signal and the input signal.
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Question 14 of 14
Calculate the phase angle of the current drawn from the AC signal source as it drives the passive integrator circuit on the left, and the active integrator circuit on the right. In both cases, assume that nothing is connected to the Vout terminal:
Reveal answerΘ = 46.7o for the passive integrator current, while Θ = 0o for the active integrator circuit.
Notes:The most important thing to be learned here is that the opamp “isolates” the signal source from whatever impedance is in the feedback loop, so that the input impedance (in this case, the 10 kΩ resistor) is the only impedance “visible” to that source. This has profound effects on the phase relationship between the output signal and the input signal.
Related Tools:
- Performance-Based Assessments for AC Circuit Competencies
- Parallel DC Circuits Practice Worksheet With Answers
