Transistor act as a switch

Posted on Feb 5, 2014

Transistor is a semiconductor device used for switching and amplification of weak signals. This article explains how a transistor work and the working of transistor as a switch. At present, transistors are applied in most of the electronic equipments for switching purposes. Digital ICs, Microcontrollers, etc uses thousands of embedded transistor f

Transistor act as a switch
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or switching. The huge electrical networks are also switched by simple transistor switching circuit (Most of the Power electronics circuits). Here we are discussing about npn transistor switching circuit. To realize the exact working principle, an LED (Light Emitting Diode) is connected to the collector of npn transistor. It glows according to the base current. Don`t forget to connect the base resistor (Rb) to limit the base current other wise the transistor become damage. Transistor switching circuits are also employed in DC Motor driver circuit Consider the first figure in which base terminal of the npn transistor is closed then the transistor is said to be in ON state (similar to a shortcircuit between Vcc and Ground) so the collector voltage is very low (0. 02V approx) Consider the second figure, When the voltage at the base terminal removed (open circuit), the transistor become OFF (means an open circuit between Vcc and Ground) then its collector voltage will be Vcc (Supply voltage)

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