Discrimination And Calculation Of Transistor

Identify the type of base and tube

Select the R*100 (or R*1K) gear of the ohm range, first connect one pin with the red test lead, and connect the black test lead to the other pin, two resistance values can be measured, and then use the red test lead to connect the other pin. , repeat the above steps, and measure a group of resistance values, so measured 3 times, there is a group of two resistance values are very small, the red test lead corresponding to this group of values is connected to the base, and the tube is PNP type On the contrary, if you use a black test lead to connect a pin, repeat the above procedure, if both measured resistance values are small, the corresponding black test lead is the base, and the tube is NPN type.

Discriminate collector

Because the β is large when the emitter and collector of the transistor are correctly connected (the needle swings greatly), and the β is much smaller when it is reversed. Therefore, first assume a collector and connect it with an ohm gear (for NPN type tubes, the emitter is connected to the black test lead, and the collector is connected to the red test lead). When measuring, hold the base and the assumed collector with your hands, and the two poles cannot touch. If the pointer swings greatly, but the pointer swings small after the two poles are reversed, it means that the assumption is correct, and the collector and emitter are determined.

Estimation of Current Amplification Factor β

Select the R*100 (or R*1K) gear of the ohm gear. For the NPN type tube, the red test lead is connected to the emitter, and the black test lead is connected to the collector. When measuring, just squeeze the base and collector with your hands (the two poles should not be in contact with each other). ), and the size of the swing of the small pointer when the handle is released, the greater the swing, the higher the β value.