Measurement methods for transistors

I. Tube identification 1. Red-to-positive, black-to-negative method: Connect the red test lead to one of the transistor’s terminals, and connect the black test lead to the other two terminals of the transistor. When the measured resistance is low (tens of Ω to a few tens of KΩ), it is of the PNP type ； When a high resistance value is measured (above a few hundred KΩ), it is of the NPN type. Moreover, the red test lead is connected to the base of the transistor. 2. Black for movement, red for fixation: This is the opposite of the method where red is used for movement and black for fixation. II. Determining the collector and emitter 1. For PNP transistors: Hold the base between the red test lead and your hand; the terminal with a lower resistance value corresponds to the collector of the PNP transistor, while the black test lead corresponds to the emitter. 2. NPN type transistors: Hold the base between the base terminal and the black test lead; the terminal with a lower resistance value corresponds to the collector of the NPN transistor, while the red test lead corresponds to the emitter. III. Determining silicon and germanium tubes: Use the R×1K range to measure the forward resistance of the emitter junction (eb) and the collector junction (cb). The forward resistance of silicon tubes is approximately 3–10 KΩ, while that of germanium tubes is around 500–1000 Ω. As for the reverse resistance of these two junctions, it is generally greater than 500 KΩ for silicon tubes, and around 100 KΩ for germanium tubes. IV. Determining whether it is a high-frequency or low-frequency tube: Use the multimeter on the R×1K setting to measure the reverse resistance between the base and emitter. If this value is several hundred kiloohms or more, then switch the meter to the R×10K setting. If the needle moves to about half of its full scale, it indicates that the tube is a silicon tube, i.e., a high-frequency tube. If the resistance value changes little, it means the tube is an alloy tube, i.e., a low-frequency tube. When measuring an NPN transistor, connect the black test lead to the emitter and the red test lead to the base ； For a PNP transistor, connect the red test lead to the emitter and the black test lead to the base.