Input and Output characteristics Determination of(a) Input resistance(b) Current amplification factor The input and output characteristics, of $\text{n-p-n}$ transistor, in its CE configuration, are as shown. (a) Typical input characteristics Input resistance$r_i = \left( \; \frac{\Delta V_{BE}}{\Delta I_B} \right)_{V_{CE}}$ (b) Typical output characteristics The relevant values can be read from the input characteristics. (b) Current amplification factor $\beta = \left( \; \frac{\Delta I_C}{\Delta I_B} \right)$ The relevant values can be read from the output characteristics, corresponding to a given value of $V_{CE}$.