Question

If the current gain of the transistor is β, what is the stability factor pertaining to IC and ICO?

(a) β+1/{1 + β * R1/(R1 + β)}

(b) β+1

(c) β+1/{1 + β * R2/(R1 + β)}

(d) β+1/{1 + (R1 + β)}

I got this question in homework.

Enquiry is from Collector Feedback Configuration in division Transistor Biasing and Low Frequencies of Analog Circuits

Answer 1

Right option is (a) β+1/{1 + β * R1/(R1 + β)}

Easy explanation: The stability factor is determined by calculating the change in IC with respect to the change in ICO. Hence, we can simply apply the method of K.V.L. and derive a relation between these two currents. After differentiation, we’ll get the stability factor as β+1/{1 + β * R1/(R1 + β)}.