# What Are The Three Poles Of The Mos Tube? How To Determine The Three Poles Of The Mos Tube?

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What Are The Three Poles Of The Mos Tube? How To Determine The Three Poles Of The Mos Tube?
The three poles of the mos tube are: G (gate), D (drain) and s (source). The voltage between the gate and the source is required to be greater than a certain value, and the drain and source can be turned on.

1. Judge the gate G
The MOS driver mainly plays the role of waveform shaping and strengthening of the drive: if the G signal waveform of the MOS tube is not steep enough, it will cause a lot of power loss during the review switching stage. The side effect is to reduce the circuit conversion efficiency, the MOS tube has a severe fever, and the MOS tube GS is easily damaged by heat. There is a certain capacitance between them. If the G signal drive capacity is not enough, it will severely affect the waveform transition time.
Short-circuit the G-S pole, select the R×1 gear of the multimeter, connect the black test lead to the S pole, and the red test lead to the D pole, and the resistance should be a few ohms to more than ten ohms. If it is found that the resistance of a pin and its two pins is infinite, and it is still infinite after exchanging the test leads, it is confirmed that this pin is the G pole, because it is insulated from the other two pins.
2. Judge the source S and drain D
Set the multimeter to the R×1k file to measure the resistance between the three pins. Use the exchange meter pen method to measure the resistance twice, and the one with the lower resistance value (generally several thousand ohms to ten thousand ohms) is the forward resistance. At this time, the black test lead is S pole, and the red one is connected to D pole. Because the test conditions are different, the measured RDS(on) value is higher than the typical value given in the manual.
3. Measure the drain-source on-state resistance RDS (on)
There is a PN junction between the source and the drain, so according to the difference between the forward and reverse resistance of the PN junction, the S pole and the D pole can be identified. For example, use a 500-type multimeter to measure an IRFPC50 VMOS tube with R×1 file, RDS(on)=3.2W, greater than 0.58W (typical value).
Test steps:
MOS tube detection is mainly to judge MOS tube leakage, short circuit, open circuit, and amplification.

The steps are as follows:
If there is a resistance value that is not tested, the MOS tube has leakage.
1. Remove the resistor connecting the gate and the source, and the red and black pens of the multimeter remain unchanged. If the needle gradually returns to high resistance or infinite after the resistor is removed, the MOS tube will leak.
2. Then a wire connects the gate and source of the MOS tube. If the pointer immediately returns to infinity, the MOS is intact.
3. Connect the red pen to the source S of the MOS, and the black pen to the drain of the MOS tube. A good needle indicator should be infinite.
4. Connect a 100KΩ-200KΩ resistor to the gate and drain, then connect the red pen to the source S of the MOS, and the black pen to the drain of the MOS tube. At this time, the value indicated by the needle is normal. If it is 0, the next charge charges the gate of the MOS tube through this resistor, generating a gate electric field, because the electric field causes the conductive channel to conduct the drain and the source, so the pointer of the multimeter deflects and the angle of deflection is large. The better the discharge performance.

Application field of MOS tube (field effect tube)
1. Industrial field, stepper motor drive, electric drill tool, industrial switching power supply
2. New energy field, photovoltaic inverter, charging pile, drone
3. Transportation field, car inverter, car HID ballast, electric bicycle
4. Green lighting field, CCFL energy-saving lamps, LED lighting power supplies, metal halide lamp ballasts
MOS tube step-down circuit

In the figure, Q27 is an N-channel MOS transistor. When pin 1 of U22A outputs high level, Q27 turns on, stepping down the VCC-DDR memory voltage to get 1.2V-HT bus power supply, and when pin 1 of U22A outputs low level, Q27 turns off , 1.2V_HT bus voltage is 0V.