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This article shows you how to analyze the application of tertiary tube and Mos tube. The content is concise and easy to understand, which will definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

1. Switching Triode

The transistors npn and pnp are used as switches and work in the cut-off zone and saturation zone (equivalent to circuit cut-off and turn-on).

When the NPN transistor is used as the switch tube, when the base Vin is low, because there is no current in the base stage, there is no current in the collector, so that the load connected to the collector has no current, which is equivalent to the switch on (off state). At this time, the transistor works in the cut off region.

In the same way, when the Vin of the base is high, because there is current flow in the base stage, the collector flows through a larger current, so the load loop is turned on, which is equivalent to the switch closed (connection state) when the transistor works in the saturation region.

Figure 1.NPN Triode is used as an example of switch tube

When the LED_DPI is high, the Triode collector and emitter are on, and the LED_DPI_TC is grounded because of the Triode conduction.

Figure 2. A switch with a combination of two transistors

The combination of two transistors can also form a switch tube, this connection is also known as Darlington transistor, the two transistors are connected in series to form an equivalent new transistor, its magnification is the product of the original two transistors, it can amplify very small signals. At the same time, it can also be used as a switch tube, and its on-off condition is the same as that of a transistor.

Darlington transistor is two transistors properly connected to form an equivalent transistor (turn on and off to the first transistor), the current magnification is the product of the two, often used in power amplifier and voltage stabilizing circuits. There are several ways to connect Darlington tube circuits: NPN+NPN,PNP+PNP,NPN+PNP,PNP+NPN, and their on-off conditions are based on the first one.

The above are all related to the NPN transistor when the switch tube.

PNP and NPN transistors do switches with similar principles, but the required logic levels are just the opposite.

Figure 3.PNP Triode Circuit Diagram when switching

In figure 3, when the base is very low, the transistor is turned on, and if it is high, the Triode is turned off.

Summary:

Transistor when the switch case, NPN transistor if you want to turn on, to input high level, if the input low level, Triode cut off. If you want to turn on the PNP transistor, you need to input a low level, and if you input a high level, the transistor is off.

Transistor as a switch technique: the transistor up arrow (emitter) in the direction of the diode only needs the diode forward turn on, then the transistor can be turned on up and down. Triode as a switch does not involve any so-called formula, magnification.

=

The transistor has the following characteristics:

IE=IB+IC

IC= β * IB (in which β ≈ 100.400)

If IB=0, then IE=IC=0

When working in the amplification area, the faintly changed electrical signal is amplified into an electrical signal with large amplitude through the Triode.

IC= β * IB (in which β ≈ 100.400)

Figure 4. Triode amplifying circuit

This circuit is also a switch tube when it is amplified to a certain state to a saturated state.

Control the forward and reverse circuit of the motor:

This circuit can control the forward rotation or reversal of the motor relative to the low power. When the R1 input high-level motor turns forward, the R2 input high-level motor reverses. The specific principle will not be repeated here.

2.mos tube on-off

On the Packaging of mos Tube and Triode

Transistor: 1B, 2E, 3C.

Mos tube: 1G, 2S, 3D.

In the figure, Q1 represents N channel and Q2 represents P channel. (the method of judgment is to remember the channel at the G gate, the arrow indicates the PN junction, and what junction corresponds to the channel position indicates the channel.)

The arrow pointing to the G pole is the N channel, and the arrow back to the G pole is the P channel, and both of their parasitic diodes are in the same direction as the arrow.

Nmos: (G extremely high level, 3V higher than S) D pole input, S pole output

Pmos: (G very low level, 3V than S pole bottom) D pole output, S pole input

When N-channel is on: Ug > Us,Ugs > Ugs (th)

When P-channel is on: Ug

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