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Signals and Switches - Technical MCQs

Q1:

Why is the given circuit called an inverter?

A The output is the opposite (inverse) of the input.

B The output is in phase with the input.

C The output is the same as the input.

D There is no output.

ANS:A - The output is the opposite (inverse) of the input.

If the input signal is high there will flow current through 1 megohm and the transistor's base-emitter junction (base, not gate). This current will be amplified, and the collector current through 1 kohm will cause a voltage drop so that the output will be low. Input high, output low.

If the input signal is low there won't be any base current, and no collector current. No current through R1 means no voltage drop, so that the output will be at +V. Input low, output high.