Question

How the current gain of a common emitter transistor amplifier expressed in terms of transistor hybrid parameters?

(a) -hfe / (1 + ZL × hre)

(b) hfe / (1 + ZL × hre)

(c) -hfe / (1 + ZL × hoe)

(d) hfe / (1 + ZL × hoe)

The question was posed to me in exam.

Origin of the question is Analysis of Transistor Amplifier Circuit using h-parameters topic in section Small-Signal Low-Frequency AC models of Transistors of Electronic Devices & Circuits

Answer 1

The correct answer is (c) -hfe / (1 + ZL × hoe)

To elaborate: The current gain of a transistor amplifier circuit is expressed as -I2 / I1. This can be expressed in terms of transistor hybrid parameters. The current gain of a common emitter transistor amplifier in terms of hybrid parameters is expressed as -hfe / (1 + ZL × hoe), where ZL is the load impedance.