The working principle of mos transistor is metal oxide semiconductor field effect transistor (mos transistor for short), which works by using the different conductivity characteristics of diffusion current and electric field between P-type region and source and drain under insulated gate. It is characterized in that:

1. The gate voltage is very low, generally between several volts and tens of volts;

2. The source-drain resistance is very large, generally above several hundred kiloohms;

3. The current is very small or zero, so it is called "zero resistance", that is, it has almost no influence on the signal;

4. The working temperature range is very wide, from-55 C to+150 C or so.

5. Excellent performance such as large magnification, low noise and low power consumption.

6. A control electrode is added to the input end of the mos tube to make the conducting state of the MOS tube controlled and stabilized. This circuit is called gated circ it or threshold circ it.

7. Add a protective diode at the output to prevent the mos tube from being damaged when the load is short-circuited.

8. mos tube has unilateral conductivity:

When a positive voltage is applied, it is in a forward bias working state; On the contrary, it is in reverse bias working state.

9. When supplying power to negative power supply, it is an open circuit if back pressure is applied to the pipe.

10. After the switch is closed, it must be reset by external force to work normally.

11. Because the driving power of mos transistor is very small (2~4w), it is very suitable for switching power supply in low frequency and high power switching devices.

12. Because the input impedance of this device is high (above 10kω), it can be made into a bipolar regulator with high voltage and high current.

13. This kind of device can be used in high frequency field because of its high input impedance (100~1000kω).

14. This kind of device has become the most popular electronic component at present because of its advantages of high withstand voltage, small volume, light weight and high reliability.

15. It is a new type of composite semiconductor device which integrates bipolar common emitter triode and complementary symmetrical triode with high power.

16. Its working principle is that the barrier between gate and source is thinned by the formation of pn junction.

17. Its advantages are high efficiency (up to 80%), strong radiation resistance and high temperature resistance.

18. However, it also has disadvantages:

(1) poor overload resistance (2) large input resistance (3) small driving power (4) high output impedance (5) high environmental requirements (6) complex manufacturing process (7) expensive (9) poor anti-interference performance (10) poor stability (11) not suitable for channel enhancer in high-power integrated circuits (2) triode triode is composed of three PNP types.