In this video we will see how to test a transistor using a digital multimeter. This video is about transistor. Transistor is a very important electronic component or device. Here at this board two transistors have been fixed. Transistor has three terminals or three pins. There are many shapes and case design of a transistor. Here the two are known as small signal transistors. Here is a little bigger transistor. This one is 2SD313 or D313 transistor used in amplifiers. We will discuss here how to test this transistor using a multi meter. There are many design and shapes of a transistor. There is one other metal flange type transistor. The number for that transistor is 2N3055 which is very commonly used in amplifiers and old UPS. That is American style transistor. That metal flange transistor 2N3055 testing is also the same way as of these small transistors. There are many types of transistor. Bipolar junction transistor, FET Field effect transistor. MOSFET metal oxide silicon field effect transistor. Which is commonly used now a days. MOSFET we shall discuss latter in some other video. Now at the moment we are discussing bipolar junction transistor BJT. BJT are very commonly used in general circuits. BJT transistor have two types. One is known as NPN and the other one is PNP. Now we will categorize these transistor on a paper to understand them well. NPN transistor is the combination of two junctions of N to P type and P to N type silicon semi conductor material. PNP transistor there are two junctions of P type to N and N type to P type semi conductor material. Symbols for NPN transistor is here. There are three terminals for a transistor. The first is base, second is collector and third is emitter. The arrow marking terminal is always referred as emitter. In NPN the arrow in the emitter is pointing outside. The PNP transistor symbol is the same as NPN, a circle and a base with collector and emitter but the arrow in the emitter will always pointing inside the base. A passive testing of a multi meter can be done on a multimeter. Active testing can be done using voltage testing of a transistor inside a circuit. A transistor is tested on multimeter as it consists of a two back to back connected diodes. To test a transistor on a multimeter one should test the two diodes connected back to back. A transistor terminals can be connected anywhere on its body. The sequence is not importantly the same for each type of transistor to the other type. The base, collector and emitter of a transistor can be located anywhere in different type of transistor. We are going to test a transistor using a digital multi meter. We will set our meter to diode range. We will test the transistor for two diodes and connect multimeter two probes to either two terminals at once. We will look for 0.7 or 0.6 volt forward voltage drop in both transistors. The terminal which is forming 0.7 or 0.6 volt with one terminal that is base. The rest of the pins are collector and emitter. Now revers or swap the probes, there will be no reading or OL on the meter. If the red probe is on the base and the other black is touched to collector and emitter simultaneously, and we get 0.7 or 0.6 means it is NPN transistor. The diode which is giving less voltage drop reading will be collector. The diode having higher voltage drop will be emitter. We are testing another transistor. We tested in the way as before but there was no reading found between any two pins. Now swap the probes together. And test again. Now as you can see the black probe is placed on base and it is commonly giving reading with collector and emitter, it is a PNP transistor. NPN and PNP transistor have different polarity. There is a different biasing for both transistor. That is the main difference between NPN and PNP types. This seems a bit difficult and confusing at first glance, but when you will follow this procedure and will grab you multimeter and transistor, this is way easy. We are going to test another available transistor which is D313 with us. If we are testing between terminals, we are getting a very close reading of Zero (0). There is no diode forming in this transistor, it is giving Zero reading from every direction. This transistor is shorted. We are testing another transistor available with us. This transistor is giving inappropriate reading from all sides between every pin. Means this transistor is also defective. Hope you people now will be able to test a transistor on a digital multimeter. It will be an easy job for you. Like the video, subscribe the channel. Thanks.