Question

Describe briefly with the help of a circuit diagram, how the flow of current carriers in a $p-n-p$ transistor is regulated with emitter-base junction forward biased and base-collector junction reverse biased.

Answer 1

The emitter base junction is forward biased with $V_{EE}$ and collector base junction is reverse biased with $V_{CC}$.

The holes in the emitter are pushed into the base by positive terminal of battery of voltage $V_{EE}$.

Base is thin and lightly doped. Hence only a few holes combine with electrons in base. Hence $I_B$ is small. Since $V_{CC}$ is large almost $99$% of holes coming from emitter are collected by collector. For each hole consumed in collector, a bond breaks in emitter and electron is released that enters positive terminal of emitter-base battery.