Question

Transistor can be used as a switch.
Reason- Both linear and non-linear voltage bias dependence occurs in it.
A. Both assertion and reason are true and reason is the correct explanation of assertion
B. Both assertion and reason are true and reason is the correct explanation of assertion
C. Assertion is true but reason is false
D. Both assertion and reason are false

Answer 1

Hint: A transistor is a semiconductor device. The electronic signals and electrical power are amplified and switched using the transistors. The emitter, base, and collector are the three terminals of the transistor. Two types of transistors are called NPN and PNP transistors.


Complete step-by-step solution:
The transistor is a combination of transfer and resistors. It means its resistance can be changed. Transistors are made up of semiconductor materials germanium and silicon. It can be used as a switch in low voltage devices like LED. Transistors can be used as switches when it is cut-off or saturated regions. It can be operated in three modes- active region, saturated region, and the cut-off region. Transistors can be used as an amplifier in the active region.

The operating conditions of the transistor are zero input base current\[\left( {{I_B} = 0} \right)\], Zero collector current\[\left( {{I_C} = 0} \right)\], and the maximum collector voltage \[\left( {{V_{CE}} = \max imum} \right)\] which results in the large depletion layer. There is no current flowing through the device. The transistor is switched to OFF. In the cut-off region, the transistor works as an OFF switch.
 In the saturated region, the transistor will be biased so that the maximum amount of base current \[\left( {{I_B} = \max imum} \right)\] is applied, resulting in maximum collector current\[\left( {{I_C} = \max imum} \right)\] and then resulting in the minimum collector-emitter voltage \[\left( {{V_{CE}} \approx 0} \right)\]drop. The depletion layer will be small in this condition. Hence, it allows maximum current to flow through it. Therefore, in the saturated regions, transistors are used as an ON switch. In the transistor, unless the current flows in the base circuit, no current can flow in the collector circuit. This property allows the transistors to work as a switch.
Hence, both assertion and reason are true and reason is the correct explanation of assertion.

Note: Integrated circuits are made up of NPN type transistors because NPN construction is cheaper, Diffusion constant is reduced, NPN construction permits higher packing of elements, P-type base is preferred.