Transistor tester circuit


Posted on Feb 7, 2014

Using the tester is easy, starting with power off, insert a transistor into the test socket. Set S1 for NPN or PNP androtate S3 to the required test position. Rotate VR1 so the desired collector emitter voltage. Pressing S2 now allows the measurement of hFE to be made. Pressing S2 and S4 allows hfe to be measured. More detailed usage now follows.


Transistor tester circuit
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With S3 in position 1, insert a transistor into the test socket and set S2 for NPN or PNP. M3 and M4 need to be shorted and a multimeter set to DC microamps between M1 and M2 now allows collector base leakage current to be measured. With silicon transistors, you may not see a reading at all, but germanium transistors have leakage current which can be measured. Set S1 for NPN or PNP and rotate S3 to position 2. Rotate VR1 so the power supply reads 6 Volt between terminal Vs and ground. Place a shorting link across M3 and M4 and a digital multimeter set to measure DC lamps across M1 and M2. Pressing S2 now allows the measurement of hFE to be made. This will be the meter reading / 20 uA. Set S1 for NPN or PNP and rotate S3 to position 3. Rotate VR1 so the power supply reads 6 Volt between terminal Vs and ground. Place a shorting link across M3 and M4 and a digital multimeter set to measure DC milliamps across M1 and M2. Pressing S2 now allows the measurement of hFE to be made. This will be the meter reading / 100 uA. Set S1 for NPN or PNP and rotate S3 to position 4. The parameter hFE varies with different collector currents and temperatures. VR1 and VR2 allow you to set up different operating points. Suppose you have a circuit where a transistor is run from a 15 Vdc supply and base current is 15 uA. First set VR1 so the power supply reads 15 Volt between terminal Vs and ground. Place a shorting link across M1 and M2 and a...




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