Question

To use a transistor as an amplifier:
(A) The emitter base junction is forward biased and the base collector junction is reverse biased
(B) No bias voltage are required
(C) Both junctions are forward biased
(D) Both junctions are reverse biased

Answer 1

Hint: Transistor is made up of the semiconductor material and is of two types as $PNP$ transistor and the $NPN$ transistor. In these transistors, the $PN$ junction diode is connected back to back with the three terminals in it as base, collector and emitter.

Complete step by step solution
The work of the amplifier is to strengthen the weak signal and the transistor is used for this purpose. In this transistor, the emitter base junction is made forward biased by connecting the voltage across it to maintain the flow of the current by maintaining the polarity of the input current.

Due to the presence of the low resistance in the input, even the small change in it, can cause appreciable change in the output current. The collector is reversely biased by connecting the voltage in the reverse direction, this makes the large voltage drop in it. Hence this makes the transistor as an amplifier by large output voltage from small input voltage.

Thus the option (A) is correct.

Note: Transistors act as both the amplifier and the switch. When using the transistor as the amplifier, it should be properly biased for work. While using the transistor as the switch, the base connecting the emitter and the collector act as the controller or switch.