Draw a circuit diagram of an n-p-n transistor amplifier in CE configuration. Under what condition does the transistor act as an amplifier?
Solution
Circuit: an n-p-n transistor in common-emitter configuration with the base-emitter junction forward biased through a base resistor and the collector connected to the supply through a load resistor RC; the signal is fed to the base. Condition for amplification: the transistor must operate in the active region, i.e. the emitter-base junction forward biased and the collector-base junction reverse biased. Under this condition a small change in base current produces a large change in collector current, giving amplification. E-B forward biased, C-B reverse biased (active region).
