Transistor Tester Circuit
The Q2 is an NPN transistor and the constant current flows into the collector lead. The value of this constant current can be given by the equation; (VD2-0.6)/(R3+R5).The POT R5 can be adjusted to get a constant current of 10uA.This constant current provided by the Q1 circuit if the transistor under test is an NPN transistor and by Q2 circuit if the transistor under test is a PNP transistor is fed to the base of transistor under test. This current multiplied by the hfe flows in the collector of the transistor and it will be indicated by the meter. The meter can be directly calibrated to read the hfe of the transistor.
Transistor Tester Circuit and Parts List
- Assemble the circuit on a general purpose PCB.
- The circuit can be powered from a general purpose PCB.
- J1 and J2 are transistor sockets.
- The Zener diodes must be rated at least 400mW.