Question

In the use of transistor as an amplifier:
(A) The emitter-base junction is reverse biased, and the collector base junction is also reverse biased.
(B) The emitter-base junction is forward biased, and the collector base junction is reverse biased.
(C) Both the junctions are forward biased.
(D) Any of the two junctions may be forward biased.

Answer 1

Hint: In this question, the concept of the transistor is used, that is the transistor can work as an amplifier by increasing the strength of a weak signal. The transistors can act as an amplifier when they are correctly biased.

Complete step by step answer:
We know that the transistor can work as an amplifier by increasing the strength of a weak signal. The transistors can act as an amplifier when they are correctly biased.

To understand the transistor as an amplifier, let us consider Figure (1). In the given figure, a transistor is connected to the circuit as an amplifier.


                                                                                   Figure (1)

As we can see in Figure (1), the input of the circuit is connected to the forward biased and the output of the circuit is connected to the reverse biased.
As we know that, to the base-emitter junction input signal or current is applied and in the given circuit the output is taken through the load in the emitter collector junction and the DC voltage is applied to the emitter-base junction.
Due to low resistance in the input circuit, there will be any small change in input signal, so the small change will be in output. So, as the small input voltage gives the large output voltage, which means that the transistor is working as an amplifier.

Therefore, in the use of transistors as an amplifier, the emitter-base junction is forward biased, and the collector base junction is also reverse biased. So, the option (B) is correct.

Note: As we know that a semiconductor device which is used to amplify or switch electric signals and electrical power is called the transistor. A transistor is a composition of semiconductor devices that is having three terminals for connection to external circuits.