Question

A transistor has hie =1KΩ and hfe=60 with an bypassed emitter resistor Re=1kΩ. What will be the input resistance and output resistance?

(a) 90kΩ and 50kΩ respectively

(b) 33kΩ and 45kΩ respectively

(c) 6kΩ and 40kΩ respectively

(d) 63kΩ and 40kΩ respectively

I have been asked this question in exam.

This interesting question is from The AC Analysis of a Small-Signal Low-Frequency Common Emitter Transistor. in division Small-Signal Low-Frequency AC models of Transistors of Electronic Devices & Circuits

Answer 1

Correct option is (d) 63kΩ and 40kΩ respectively

Easiest explanation: As the emitter is bypassed, the input resistance Ri=hie

=1kΩ. The output resistance RO=1/hoe but the value is not given.

So, hoe=0 and RO=1/0=∞.