Transistors used in electronics circuits

Transistors used in electronics circuits

Transistor is perhaps the most important of electronic components because of which all modern electronics works. A transistor is a semiconductor device commonly used to amplify or switch electronic signals. It’s a Device with three terminals where one terminal can be use to control the flow of current through the other two terminals. The three terminals are Emitter, Base and Collector. Its major use is as amplifier to boost various signals as well as to perform automatic switching.

There are 2 types of transistors

NPN


When base of n-p-n is connected with logic high voltage (positive voltage) then it short circuits emitter and collector (SWITCH ON). When base of n-p-n is connected with logic low voltage (Ground of Supply) then it open circuits both emitter and collector (SWITCH OFF).

PNP


When base of p-n-p is connected with logic high voltage then it opens circuit’s emitter and collector (SWITCH OFF). When base of p-n-p is connected with logic low voltage then it short circuits both emitter and collector (SWITCH ON).

Another point you should keep in mind is that the arrow always points in the direction of positive charge flow, or from the P to N sections, no matter whether the P section is the emitter or base.

Notation aside, the three pins – base, emitter, collector – are typically labeled on the data sheet for a transistor

Connection for N-P-N transistor


  • Device power to whatever power source I want to use
  • Device ground to the collector on my NPN transistor
  • Transistor emitter to “real” ground.

Connection for PNP transistor


Example of Transistor with Buzzer


Commonly used Transistors and their pin identifications

BC548/BC547 :– NPN

BC557 :– PNP

2N3904 :– NPN 

SL100:– NPN