Transistor Tester
This simple circuit has helped me out on many occasions. It is able to check
transistors, in the circuit, down to 40 ohms across the collector-base or base-emitter
junctions. It can also check the output power transistors on amplifier circuits.
Circuit operation is as follows. The 555 timer ( IC1 ) is set up as a 12hz multi
vibrator. The output on pin 3 drives the 4027 flip-flop (IC2). This flip-flop
divides the input frequency by two and delivers complementary voltage outputs to
pin 15 and 14. The outputs are connected to LED1 and LED2 through the current
limiting resistor R3. The LED's are arranged so that when the polarity across
the circuit is one way only one LED will light and when the polarity reverses
the other LED will light, therefore when no transistor is connected to the
tester the LED's will alternately flash. The IC2 outputs are also connected to
resistors R4 and R5 with the junction of these two resistors connected to the
base of the transistor being tested. With a good transistor connected to the
tester, the transistor will turn on and produce a short across the LED pair. If
a good NPN transistor is connected then LED1 will flash by itself and if a good
PNP transistor is connected then LED2 will flash by itself. If the transistor is
open both LED's will flash and if the transistor is shorted then neither LED
will flash.
Also check the conversation about this project at the community. Post you questions here.
Title: Transistor Tester
electronic circuit
Source: www.electronics-lab.com
Published on: 2005-02-10
Reads: 1405
Print version:
Other electronic circuits and schematics from Test and measurement
-
Digital Voltmeter
-
Voltage follower with 1G ohm input resistance
-
1GHz Simple Frequency Counter
-
XTal Tester
-
Capacitance Meter
-
Crystal Tester
-
Linear Resistance Meter
-
IR Remote Control Tester
-
Mosfet TESTER
-
Continuity Tester