Summary of the conduction conditions of transistors

The understanding of the amplification of the transistor, remember one thing: energy does not produce for no reason, so the transistor must not produce energy.

But what makes the transistor so powerful is that it can control large currents by small currents.

The principle of amplification is that the large static DC is controlled by a small AC input.

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

So, the usual work flow is, whenever the water, people open the small valve, very small flow trickling out, this trickle impact large valve switch, large valve opened, the surging river flow.

If you keep changing the size of the small valve opening, then the large valve will also change accordingly, if it can be strictly proportional change, then the perfect control is complete.

Here, Ube is a small water, UCE is a big water, people are the input signal. Of course, it would be more accurate if the current were to be compared to electricity, since the transistor was, after all, a current control element.

If one day, the weather is very dry, the river is not, that is, the big water is empty. This time the administrator opened the small valve, although the small valve still hit the big valve, and make it open, but because there is no current, so, and no water out. This is the cutoff area in the transistor.

The saturation zone is the same, because at this time the river reached a large and large extent, the size of the valve opened by the administrator has been useless. If the valve does not open the river itself burst, this is the breakdown of the diode.

In analog circuits, the general valve is semi-open, by controlling its opening size to determine the size of the output flow. When there is no signal, the water flow also flows, so, when not working, there will be power consumption.

In the digital circuit, the valve is open or closed in two states. When not working, the valve is completely closed, without power dissipation.

For NPN tubes, when UB > UE, and Ub-ue >0.5v, UC > UB, the transistor is in the amplification area (Uc>ub>ue)

When UB > UE, UB > UC, the transistor is in saturation zone

Transistors are in the cutoff area when UB < UE, UB < UC

For PnP tubes, when UB < UE, and Ub-ue <0.5v, UC < UB, transistors are in the magnification zone (uc<ub<ue)

When UB < UE, UB < UC, the transistor is in saturation zone

Transistors are in the cutoff area when UB < UE, UB > UC