Easy way to Test Transistor is working or Not .

The purpose of the transistor tester circuit is to test the NPN or PNP transistor whether they are working fine or not.So,i decided to provide you the simplest circuit that can be built on breadboard.I think this is the most simplest circuit ever to test the transistor and it works fine.You just need to place the transistor to check it and press the button.That’s all.If LED blinks by pressing the button your transistor is not faulty.

 --> The circuit consists of few resistors,LED and buzzer.There are two circuits.One to check NPN transistor and the other to check PNP transistor

As you know transistor can also work as a switch.Here this property of transistor is used to check the transistor.If we see the NPN transistor tester,the base pin is connected to button via series resistor of 10k. The button when pushed connects the two points and the voltage (3V) reaches the base pin of NPN transistor (that needs to be checked).10k resistor simply reduces the base current.Transistor gets ON when button is pushed (if the transistor is not faulty) and the LED will glow and the buzzer makes sound. "If transistor is faulty then LED

will not glow on pushing the button or LED will glow without pushing the button".....!!!!!!!
The principle of PNP transistor tester is same as the NPN transistor tester.The difference is just the placement of components.As PNP transistor turns ON when its base voltage is less than 0.6V. So,By pushing the button,PNP transistor (that needs to be checked) turns ON and LED glows as well as buzzer.The whole circuit uses only one supply that can be provided to the circuit using 3V cell.                                                                                                                      

Components:

R1,R3 270 ohm (1/4watt)
R2,R4 10k (1/4watt)
D1,D2 LED (green)
BZ1,BZ2 buzzer
Push Button x 2

Note:

"If transistor is faulty then LED will not glow on pushing the button or LED will glow without pushing the button  "