In a silicon transistor, base current is changed by `20muA`. This result in a change of `0.02V` in base-emitter voltage and a change of `2 mA` in the collector current.
Find the input resistance, `beta_(a.c.)` and transconductance of the transistor.
The transistor is used as an amplifier with the load resistance `5k Omega`. What is the voltage gain of the amplifier?

Explanation

(i) `r_(i)=(Delta V_(BE))/(Delta I_(B) )=(0.02)/(20xx10^(-6)) = 1k Omega`, `beta_(ac)=(Delta I_(C))/(Delta I_(B) )= (2xx10^(-3))/(20xx10^(-6))=100` (ii) Voltage gain, `A_(v) =-g_(m)R_(L)=-(0.1)(5xx10^(3))=-500`.(since, `g_(m)=(beta _(ac))/(r_(i)))`