FCC Exam Question: 8-23C3

In video amplifiers, compensation for the input and output stage capacitances must be accomplished to prevent distorting the video pulses. This compensation is normally accomplished by connecting:

A. Inductors in parallel with both the input and output capacitances.
B. Resistances in parallel with both the input and output capacitances.
C. An inductor in parallel with the input capacitance and an inductor in series with the output capacitance.
D. An inductor in series with the input capacitance and an inductor in parallel with the output capacitance.
Correct Answer: D

Explanation: Video amplifiers require a wide bandwidth to accurately reproduce high-speed video pulses. Internal and parasitic capacitances at the input and output stages naturally limit the amplifier's high-frequency response, causing distortion like rounded edges in pulses. To counteract this: * **At the input:** An inductor connected *in series* with the signal path, effectively before the input capacitance, creates a series resonant circuit. At higher frequencies, this series peaking boosts the signal, compensating for the input capacitance's tendency to roll off the high frequencies. * **At the output:** An inductor connected *in parallel* with the output capacitance forms a parallel resonant circuit. At the target high frequencies, this parallel (shunt) peaking provides a high impedance, preventing the output capacitance from shunting the signal to ground and maintaining the amplifier's gain. This combination (series inductor at input, parallel inductor at output) is a standard technique for broadband amplifier compensation, extending the frequency response and preventing pulse distortion. Options A, B, and C either use incorrect components (resistances) or incorrect inductor placements for effective compensation.

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Includes Elements 1, 3, 6, 7R, 8, and 9.