Thursday, November 4, 2010

WOW-DESIGN TECHNIQUES- Transistor As An Electronic Switch

This section demonstrates a design technique for Transistors used as an electronic switch. For many years as an electronics hobbyist, I used this method in all of my circuit designs. This is the same principle applied by most of the engineers. For the beginners, it is a lot of help developing ideas on how do engineers design electronics circuits. For the engineers, this might give you a review for it.

This circuit is widely seen and very common in many applications especially controlling a certain task electronically.

I am using NPN transistor as an example. The objective of this design is to make the transistor as an electronic switch. In this instance, the “LOAD” component, DC voltage power supply or VCC, and input voltage are given or VIN. To find the actual values and power rating of RC and RB are the goal of the design.

The resistor RC is necessary when the amount of load current is to be only limited below the Collector current rating of any transistor. The resistor RB is calculated to ensure that a very small amount of Base current enough to turn ON the transistor. Turning ON the transistor electronically, it means the transistor is saturated. Saturation of the transistor occurs when a presence of a small current at the Base. It is made also that voltage across Collector and Emitter approximately zero volts and at this point it is acting like a switch closed or Closed circuit. Transistor is cut-off or turn OFF only where there is an absence of voltage applied from the Base.


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