How to use and function of the triode, the role of the triode

Amplification, modulation, resonance, switching.

The working state of the transistor in the circuit:

The transistor has three working states: cut-off state, amplification state, and saturation state. When the transistor is used for different purposes, its working state is different.

1. Cut-off state: when the working current of the triode is zero or very small, that is, IB=0, the IC and IE are also zero or very small, and the triode is in the cut-off state.

2. Amplification state: In the magnification state, ic= ib, where the size (magnification) is basically unchanged (the characteristic of the magnification area). If there is a base current, there is a collector current corresponding to it.

3. Drinking and state: In the drinking and harmony state, when the base current increases, the collector current does not increase much, and when the base current increases further, the collector current almost no longer increases.

Cut-off status. The resistance between collector and emitter is very large IB=0 or very small, IC or IE is zero or very small because IC IB

The triode can be judged to be in a cut-off state by using the fact that the current is zero or very small.

Zoom in on the state. The internal resistance between the collector and the emitter is controlled by the magnitude of the base current, and the base current is large, and its internal resistance is small IC IB

ie=(1+β)ib

If there is a base current, there is a corresponding collector current and emitter current, and the base current can effectively control the collector current and emitter current.

Saturated. The internal resistance between the collector and the emission is very small, the current of each electrode is very large, and the base current can no longer control the collector current and the emitter current, and the current amplification factor is very small, even less than 1

A way to control the signal with direct current).

1. Current amplification:

The transistor is a current control device, which uses the base current IB to control the collector current IC and emitter current IE, without IB there is no IC and IE, as long as there is a small IB, there is a large IC. In the amplification circuit, this characteristic of the transistor is used to amplify the signal.

2. Switch function:

When the transistor is switched, it works in two states: cut-off and saturation.

In the triode switching circuit, the collector and emitter of the triode are equivalent to a switch, and the internal resistance between the collector and the emission is very large when the triode is cut off, which is equivalent to the disconnected state of the switch; When the transistor is saturated, the internal resistance between the collector and the emitter is very small, which is equivalent to the switch-on state.

The amplification function (when working, the transistor works in the amplification area) is used to form an amplification circuit.

2.Electronic switching action (when working, the transistor works in the saturation zone and cut-off zone).

The transistor has a current amplification effect, and its essence is that the transistor can control the large change of collector current with a small change in the base current. This is the most basic and important characteristic of a transistor. We refer to the ratio of δic δib as the current amplification of the transistor and is denoted by the symbol " ".

The current amplification factor is a fixed value for a certain transistor, but it will also change to a certain extent as the triode works as the base current changes.

Triode is also very common in circuits, and it is also widely used, such as used as a switch control, used as a signal shed for large leakage amplification, etc., these are the functions of the triode, what are the functions of the triode?

It is commonly used as a switch, because the output current of the IO port of the single-chip microcomputer is limited, generally about 10mA, if it is used to drive a slightly larger device, such as a buzzer or LED, you need to add a triode behind the IO port to control. If you encounter a chain of higher power devices, or control other alternating current power supplies, at this time, a triode is needed to drive the relay, and the relay will then control the high-current equipment to form a two-stage drive.

The transistor has the function of amplifying the signal, which is also an important feature of the transistor, and the triode is often used in the audio signal to amplify the weak audio. The transistor can also be used to reverse, for example, in some special cases, the output of the microcontroller is a positive voltage control negative voltage device, or a negative voltage control positive voltage device, so that reverse control is required, and a triode is needed.