Quickly understand and identify MOS tubes in one minute

Some friends said that they have studied MOS for a long time, but they still can't understand it clearly. Is it really that difficult?

Today we will use the simplest way to explain how to understand MOS tubes.

How to identify the three poles:

We know that MOS tubes have three poles.

Gate (G), the gate is the easiest to recognize

Source (S): Whether it is a P channel or an N channel, the intersection of the two lines is the source;

Drain (D): Whether it is a P-channel or an N-channel, one side of the separate lead is the drain.

These three pins are used to connect external circuits.

G pole: used to control the pin. By changing the level of the pin, the on and off of the MOS tube can be directly controlled;

The D pole and the S pole, these two pins, are equivalent to the two ends of the switching circuit, one connected to the power supply and the other connected to the circuit ground.

How to distinguish P channel?

It's very simple, let's look at the principle icon:

The arrow facing away from the G pole is the P channel

The arrow pointing to the G pole is the N channel

Direction of parasitic diode

The arrow pointing from the S pole to the D pole is the N channel

The arrow pointing from the D pole to the S pole is the P channel

This parasitic diode plays a big role when the MOS tube is used for circuit isolation.

One is that when VDD is over-voltage, the diode breaks down in reverse and directs the large current to the ground to prevent the MOS tube from burning out.

The other is to prevent the MOS tube from burning out when the source and drain are reversely connected, or to provide a path for the reverse induced circuit when the circuit is reverse induced by voltage, thereby preventing the MOS tube from being broken down.

As long as you understand the basic principles, MOS tubes will be much easier to use.

Well, that’s all for this issue.