Question

How do we compute the output impedance of a simplified CC amplifier?

(a) RE || (re‘ – (R1 || R2) / (β + 1))

(b) RE || (re‘ – (R1 || R2) / (β – 1))

(c) RE || (re‘ + (R1 || R2) / (β + 1))

(d) RE || (re‘ + (R1 || R2) / (β – 1))

This question was addressed to me by my school teacher while I was bunking the class.

This interesting question is from Simplified Calculations for the CC Configuration in portion Low Frequency Transistor Amplifier Circuit of Electronic Devices & Circuits

Answer 1

Correct choice is (c) RE || (re‘ + (R1 || R2) / (β + 1))

Easiest explanation: The output impedance of a simplified common collector (CC) amplifier can be expressed in terms circuit resistor values. The base impedance is RE || (re‘ + (R1 || R2) / (β + 1)) . Where β is the transistor amplifiers current gain, Re is the equivalent emitter resistance and re‘ is the alternating current resistance of the emitter-base diode.