# 11 Essential Knowledge Points About Mos Tube If You Don't Read Them, You'll Be Missing A Lot

2023-05-02Archive

1. Tripolar Judgment

G gate (gate) - gate, of course, they are easier to recognize; S pole (source) - source, whether it is P channel or N channel, two lines intersect; D (drain) - sink, whether it is P-channel or N-channel, is side of a single output.

2. Difference between N-channel and P-channel

The arrow pointing to G pole is N-channel, and arrow pointing away from G pole is P-channel.

3. Determining direction of parasitic diode

Regardless of whether N-channel or P-channel MOSFETs, direction of arrow of intermediate substrate and direction of arrow of parasitic diode are always same: either all point from S to D, or both point to S.

4. Functions implemented by MOS switch

1>Signal switching

2>Power on and off

5. Connection method in circuit when MOS tube is used as a switch

Highlights:

1> Determine which pole is connected to input terminal and which pole is connected to output terminal. 2> What is level of control pole? When V, MOS tube turns on 3> What is level of reference electrode? MOS tube cut at V

NMOS: D-pole connected to input, S-pole connected to output PMOS: S-pole connected to input, D-pole connected to output

NMOS if: S connected to input, D connected to output

Because parasitic diode is directly connected, S pole voltage can be unconditionally transferred to D pole, and MOS tube loses its switch function.

If PMOS: D connected to input, S connected to output

The function of switch is also lost.

6. MOS lamp switching conditions

N channel — at Ug> Us,Ugs> Ugs(th) when conducting; P channel — when running Ug< Us,Ugs< Ugs(th) when running. In short, conduction condition: |Ugs|>|Ugs(th)|

7. Related concepts

BJT:Bipolar Junction Transistor The bipolar transistor, BJT, is a current control device.

FET:Field-effect transistor A field-effect transistor (FET) is a voltage control device. By structure, field-effect transistors are divided into: junction field-effect transistors (denoted JFET), insulated gate field-effect transistors (denoted as MOSFET).

Two categories:

According to channel material: junction type and insulated gate type are divided into N-channel and P-channel;According to conduction mode: depletion type and amplification type, junction FETs are classified as depletion type, FETs with an insulated gate are both depleted and amplified.

In general, FETs can be divided into junction FETs and MOSFETs, and MOSFETs are divided into N-channel depletion type and enhancement type; P-channel depletion type and enhancement type are four kinds. .

8. Important parameters of MOS tube

①Package

②Type (NMOS, PMOS) ③Withstand voltage Vds (maximum④Saturation current Id ⑤Turn-on resistance Rds ⑥Gate threshold voltage Vgs(th)

9. Identify pins from MOS tubes

Whether it is NMOS or PMOS, place it in direction shown in picture above, middle leg is D, left leg is G, and right leg is S.

Or write this: single leg D, rotate DGS counterclockwise.

By way, I would like to note identification of pins of triode: also align according to direction in figure above, middle pin C, left B and right E.

Pin:

Start at pin G, 123 counterclockwise, and triode pin numbers also start at pin B, 123 counterclockwise.

10. Use a multimeter to determine NNOS and PMOS

Separation using parasitic diodes. Turn multimeter gear to diode gear, connect red probe to S, and black probe to D, if there is a numeric display, and vice versa, if there is no value, then it is N-channel, and if situation is reversed, then P-channel.

11. Draw MOS tube