Question

What is the stability factor against VBE for the collector feedback configuration?

(a) β/(Rc * (1 + β))

(b) -β/(RB + Rc * (1 + β))

(c) β/(RB + Rc * (1 + β))

(d) -β/(Rc * (1 + β))

I have been asked this question during an online interview.

My question is from Collector Feedback Configuration in section Transistor Biasing and Low Frequencies of Analog Circuits

Answer 1

The correct option is (c) β/(RB + Rc * (1 + β))

To explain: This is easily derived from the Collector feedback configuration by using the method of K.V.L. deriving a relation between the collector current and the base emitter voltage. It should be noted that the stability against VBE increases in comparison to the base bias comparison.