Question

In a given common Emitter transistor, Emitter current is changed by $2.1mA$ . This results in a change of $2mA$ in the collector current and a change of $0.05V$ in the Emitter-base voltage. The input resistance (in ohm) is :-

Answer 1

Answer: 500

$\Delta I_E=\Delta I_B+\Delta I_C$
$2.1=\Delta I_B+2\Rightarrow \Delta I_B=0.1mA$
$v_{\text{in }}=\Delta I_B{R}_{\text{in }}$
$0.05=10^{-4}{R}_{in}$
$R_{\text{in }}=500\Omega$