Question

What is the approximate hybrid parameter input resistance of a CC amplifier?

(a) hie – (1 + hfe) × RL

(b) hie + (1 + hfe) × RL

(c) hie – (1 + hfe) / RL

(d) hie + (1 + hfe) / RL

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This key question is from Approximate Hybrid Model and its use in CE, CB, CC topic in portion Small-Signal Low-Frequency AC models of Transistors of Electronic Devices & Circuits

Answer 1

Correct answer is (b) hie + (1 + hfe) × RL

To explain: The input resistance of a common collector (CC) amplifier can be expressed in terms of approximate hybrid parameters. The input resistance is hie + (1 + hfe) × RLwhere, hie and hfe are the input resistance and current gain of CE amplifier respectively and RL is the load resistance.