In a silicon transistor, the base current is changed by `20muA`. This results in a change of 0.02 V in base to emitter voltage and a change of 2mA in the collector current.
Find the input resistance, `beta_(ac)` and transconductance of the transistor `g_m`.

Explanation

Change in base current `= Delta I_(b)= 20 mu A`
Change in base emitter voltage `=Delta I_(i)= 0.02V`
Change in collector current `= Delta I_(c )= 2mA`
input resistance `=R_(i)= (Delta V_(i))/(Delta I_(b))`
`=(0.02)/(20 xx 10^(-6))`
`=(2)/(2000) xx 10^(6)= 10^(3) Omega`
`R_(i)= 1k Omega`
Current gain `=beta_(ac)= (Delta I_(c))/(Delta I_(b))`
`=(2 xx 10^(-3))/(20 xx 10^(-6))= (10^(3))/(10) = 10^(2)= 100`