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Inverting and Noninverting OpAmp Voltage Amplifier Circuits
41 questions By Tony R. Kuphaldt
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Question 28 of 41
Calculate the output voltage of this op-amp circuit (using negative feedback):
Also, calculate the DC voltage gain of this circuit.
Reveal answerVout = -8.1 volts
AV = 5.4
Follow-up question: the midpoint of the voltage divider (connecting to the inverting input of the op-amp) is often called a virtual ground in a circuit like this. Explain why.
Notes:It is important that students learn to analyze the op-amp circuit in terms of voltage drops and currents for each resistor, rather than just calculate the output using a gain formula. Detailed, Ohm’s Law analysis of op-amp circuits is essential for analyzing more complex circuitry.
The “virtual ground” question is an important one for the sake of rapid analysis. Once students understand how and why there is such a thing as a “virtual ground” in an op-amp circuit like this, their analysis of op-amp circuits will be much more efficient.
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Question 29 of 41
Calculate the voltage gain for each stage of this amplifier circuit (both as a ratio and in units of decibels), then calculate the overall voltage gain:
Reveal answer- Stage 1:
- AV = 1.5 = 3.522 dB
- Stage 2:
- AV = 1.545 = 3.781 dB
- Overall:
- AV = 2.318 = 7.303 dB
Notes:Not only does this question review calculation of voltage gain for inverting amplifier circuits, but it also reviews decibel calculations (for both single and multi-stage amplifiers). Discuss how the decibel figures for each stage add to equal the total decibel gain, whereas the ratios multiply.
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Question 30 of 41
Calculate the voltage gain for each stage of this amplifier circuit (both as a ratio and in units of decibels), then calculate the overall voltage gain:
Reveal answer- Stage 1:
- AV = 1.766 = 4.940 dB
- Stage 2:
- AV = 0.455 = -6.848 dB
- Overall:
- AV = 0.803 = -1.909 dB
Notes:Not only does this question review calculation of voltage gain for inverting amplifier circuits, but it also reviews decibel calculations (for both single and multi-stage amplifiers). Discuss how the decibel figures for each stage add to equal the total decibel gain, whereas the ratios multiply.
