Question

Draw a typical output characteristics of an $n-p-n$ transistor in a $CE$ configuration. Show how these characteristics can be used to determine output resistance.

Answer 1

Output characteristics is the plot between collector emitter voltage $V_{CE}$ and the collector current $\left(I_C\right)$ at different constant values of base current $\left(I_B\right)$.


Output resistance is defined as the ratio of the change in collector-emitter voltage $\left(\Delta V_{CE}\right)$ to the change in collector current $\left(\Delta I_C\right)$ at a constant base current $\left(I_B\right)$.
The reciprocal of slope of the linear part of the curve gives the value of output resistance i.e., $r_0={\left(\frac{\Delta V_{CE}}{\Delta l_C}\right)}_{I_B}$