Simple Transistor Tester
Transistors are discrete electronics device majorly used for amplifying signal. However inn using this semiconductor, some experience difficulty in identifying the real pin out of this 3-terminal semiconductor device.
The testing can be grouped as;
1. Distinguishing an NPN from a PNP type transistor
2. Identifying the Base, Emitter and Collector of all small signal type transistor
3. Testing and Identifying a faulty transistor
1. Distinguishing an NPN from a PNP transistor
Finding the base of a transistor using an Analog multimeter
Get an unknown transistor and test it with a multimeter (analog) set to "x10"
Place the BLACK(negative) probe on a pin and the RED(positive) probe on the two other pins and observe the swing on the multimeter. If the meter swings nearly full scale for the six combinations. Then you have a PNP type transistor.
The terminal at which the BLACK probe is kept stationary is the BASE of the transistor.
NOTE:After identifying the BASE of the transistor. Place the probes (RED and BLACK) on the other two pins of the transistor. If it gives a nearly full swing then, the transistor is FAULTY
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| PNP type transistor |
2. Get an unknown transistor and test it with a multimeter (analog) set to "x10"
Place the RED (positive) probe on a pin and the BLACK (negative) probe on the two other pins and observe the swing on the multimeter. If the meter swings nearly full scale for the six combinations. Then you have a NPN type transistor.
The terminal at which the RED probe is kept stationary is the BASE of the transistor.
NOTE: After identifying the BASE of the transistor. Place the probes (RED and BLACK) on the other two pins of the transistor. If it gives a nearly full swing then, the transistor is FAULTY
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| NPN type transistor |
Set the meter to "x10k."
For an NPN transistor, place the leads on the transistor and when you press hard on the two leads shown in the diagram below, the needle will swing almost full scale.
For a PNP transistor, set the meter to "x10k" place the leads on the transistor and when you press hard on the two leads shown in the diagram below, the needle will swing almost full scale.
Identifying an NPN type transistor using a digital Multimeter
1. Put the meter in diode mode
2. Keep the positive probe to the Base pin of the transistor.
3. Touch the negative probe to the right pin. You will see a reading on the multimeter.
4. Similarly touch the negative probe to the left pin with respect to BASE pin. You will see a reading on the multimeter.
5. It will ensure that it is a NPN transistor.
However, in identifying the base of transistor using a digital multimeter. The same procedure used in the analog section will be used the only alteration is that the knob of the meter will be tuned to Ohms range (2k).
Also, to identify a faulty transistor using a digital multimeter is very simple. After identifying the base of the transistor, the probe of the transistor (RED and BLACK) is placed on the other two pin of the transistor with the meter set at Ohms range (2k) If there is a reading on the meter, then the transistor is faulty. It should give a null or 0 reading on the meter.
The logic behind this is, in NPN transistor
Emitter (E) – N type material – Equivalent to cathode of the diode
Base (B) – P type material – Equivalent to anode of the diode
Collector(C) – N type material – Equivalent to cathode of the diode
If the multimeter positive probe is connected to anode and negative probe is connected to cathode, then it will show voltage. If the connections are interchanged it will not show any value.
Quite interesting
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