Understanding Transistors in One Article

1. Circuit symbol of transistor

Classification of transistors

a. According to frequency: high frequency tube and low frequency tube

b. According to power: small power tube, medium power tube and high power tube

c. According to the structure: PNP tube and NPN tube

d. According to the material: silicon tube and germanium tube

e. By function: switch tube and amplifier

3. Use a multimeter to determine the polarity and type of the semiconductor transistor (using a pointer multimeter)

a. First select the range: R﹡100 or R﹡1K.

b. Determine the base of semiconductor transistor:

Use the black probe of the multimeter to fix one electrode of the transistor, and connect the red probe to the other two electrodes of the semiconductor transistor respectively. Observe the deflection of the pointer. If the measured resistance values ​​are both large or both small, the pin connected to the change is the base (the one with both small resistance values ​​is an NPN type tube, and the one with both large resistance values ​​is a PNP type tube). If the two measured resistance values ​​are one large and one small, use the black pen to re-fix one pin of the semiconductor transistor and continue measuring until the base is found.

c. Identify the c-pole and e-pole of the semiconductor transistor:

After determining the base, for the NPN tube, use the two probes of the multimeter to connect the other two poles of the transistor, and measure twice alternately. If the results of the two measurements are not equal, the one with the smaller resistance value means that the black pen is connected to the e pole and the red pen is connected to the c pole (if it is a PNP tube, the electrodes connected to the black and red probes are opposite).

d. Determine the type of semiconductor transistor.

If the base of a semiconductor transistor is known, you can connect the red test lead to the base and use the black test lead to measure the other two electrode pins respectively. If the measured resistance value is very large, the transistor is an NPN type semiconductor transistor. If the measured resistance values ​​are very small, the transistor is a PNP type semiconductor transistor.

4. Detection of the quality of semiconductor transistors

a. Select the range first: R﹡100 or R﹡1K

b. Measure the forward resistance of the emitter and collector of the PNP type semiconductor transistor.

Connect the red test lead to the base and the black test lead to the emitter. The measured resistance is the forward resistance of the emitter. If the black test lead is connected to the collector (the red test lead remains unchanged), the measured resistance is the forward resistance of the collector. The smaller the forward resistance value, the better.

c. Measure the reverse resistance value of the emitter and collector of the PNP type semiconductor transistor.

Connect the black test lead to the base and the red test lead to the emitter and collector respectively. The measured resistance values ​​are the reverse resistance of the emitter and collector respectively. The smaller the reverse resistance, the better.

d. The method for measuring the forward resistance of the emitter and collector of an NPN type semiconductor transistor is opposite to the method for measuring a PNP type semiconductor transistor.