Transistor principle of popular talk

The understanding of the role of transistor amplification, remember that: the energy will not be generated for no reason, so the transistor must not produce energy.

But the triode is awesome: it can control high current with small current.

The principle of amplification is that: through a small AC input, control of large static DC.

Assuming that the transistor is a dam, the weird part of the dam is that there are two valves, one big valve and one small valve. Small valves can be opened with manpower, large valves are heavy, manpower is not open, only through the hydraulic valve to open.

Therefore, the usual work flow is that when the water is drained, people open the small valve and a small flow of water flows out slowly. This trickle blows the switch of the large valve, the large valve opens, and the surging river flows down.

If you constantly change the size of a small valve open, then the large valve also kept changing accordingly, if strictly scaled to change, then, the perfect control is completed.

Here, Ube is a small stream, Uce is a big flow, people are the input signal. Of course, if the current is compared to the current, it will be more precise, because the transistor is a current control element, after all.

Cut-off area: It should be that the small valve is not enough to open, you can not open the valve, this is the cut-off area.

Saturated zone: It should be a small valve to open too much, so that the water flow in the large valve has reached its limit of flow, but you turn off the small valve, you can make the transistor work from the saturation zone back to the linear zone.

Linear zone: Is the flow in an adjustable state.

Breakdown zone: For example, there is a water flow in a reservoir, the water level is too high (corresponding to Vce too), resulting in a gap, the water flow out. Moreover, with the small valve open, the breakdown voltage becomes lower, it is easier to breakdown.

Term Description

First, the transistor

Transistor is the two PN junction common in a semiconductor material, because each semiconductor transistor has two PN junction, it is also known as the bipolar junction transistor.

Transistor is actually the same two diodes connected. It is the current control element, the use of a narrow base of the special structure, through the carrier diffusion and recombination, to achieve the base current collector current control, so that the transistor has more control. In accordance with the internal structure to distinguish, the transistor can be divided into PNP tube and NPN tube, two tubes connected in accordance with a certain way, you can form a pair of tubes, with more ability to work. If the difference according to the power consumption of the transistor, they can be divided into small power transistor, the power transistor, power transistor and so on.

Second, the role and application

Transistor with current signal amplification and switching control role. Therefore, the transistor can be used to amplify the signal and control the current on and off. In power, signal processing and other places can be seen in the transistor, integrated circuits are also by many transistors in accordance with a certain form of circuit connected, with certain components. Transistor is the most important current amplification components.

Third, the transistor of the important parameters

1, β value

The value of β is the most important parameter of the transistor, since the value of β describes the size of the transistor's ability to amplify the current signal. The higher the value of β, the stronger the ability of amplifying the small signal, and vice versa; but the value of β can not be very large. Because the performance of the transistor is not stable, the value of β should usually be 30 to 80. In general, the beta value of a transistor is not a specific one and it generally varies slightly depending on the operating condition of the device.

2, the very reverse current

The smaller the reverse current between the poles, the higher the stability of the transistor.

3, the transistor reverse breakdown characteristics:

Transistor consists of two PN junction, if the reverse voltage exceeds the rated value, it will be like a diode breakdown, the performance degradation or permanent damage.

4, the working frequency

The value of the transistor β only in a certain range of operating frequency remains unchanged, if the frequency range beyond, they will fall sharply with increasing frequency.

Fourth, classification

According to the principle of amplification, the transistors are divided into BJT (Bipolar Junction Transistor) and unipolar (MOS / MES: Metal-Oxide-SemIConductor or MEtal Semiconductor) transistors. There are two carriers in the BJT that participate in the conduction, whereas in the MOS type there is only one kind of carrier conduction. Usually a current BJT control member, the control voltage is typically a MOS type device.

Five, use

Engage in the use of digital circuits Most of the transistor switch, as long as the transistor to ensure that the work in the saturation zone and the cut-off area can be.