Analysis of transistor working principle

For PN Junction, in P region, the hole is a multi-sub, the electron is a small child.

In the N region, electrons are multi-sons, and holes are small children.

Figure 1 Positive deviation of PN Junction

Figure 2 pn Junction Inverse bias

When the PN Junction is biased, the majority of carriers are electrically conductive, and the minority carriers are electrically conductive when reverse biased. Due to the small number of carriers, the reverse bias current is smaller, and the PN junction shows the single-phase electrical resistance. If you want to think of increasing the reverse leakage current, as long as the way to increase the number of anti-biased minority carriers (such as the principle of light-sensitive diodes). In particular, the inverse of the minority carrier reverse through the PN is very easy, and even more than the positive bias when the majority of carriers forward through the PN junction is easier.

Within the PN Junction there is an internal electric field due to the diffusion of the majority of carriers, and the direction of the internal electric field is always hindered the majority of the carrier forward through, so, the majority of carriers forward through the PN junction need to overcome the role of the internal electric field, the need for about 0.7V of the external voltage, which is the PN junction is the gate voltage While the reverse bias, the internal electric field under the action of the Power will be strengthened, that is, the PN knot thickening, a small number of carriers reverse through the PN Junction, the internal electric field and a small number of carriers through the PN junction direction of the same, that is, at this time the internal electric field to a small number of carriers through stepping will not hinder the role This leads us to the conclusion that the reverse-biased minority carriers are easily reversed through the PN Junction, which is even easier than when most carriers are moving through the PN junction.

Take the NPN type as an example.

After the transmit junction plus the positive bias voltage conduction, under the action of the applied voltage, most of the carrier-electrons in the transmitting area are easily transmitted into the base area. Once these carriers enter the base area, their properties in the base region (P) still belong to minority carriers. As mentioned earlier, it is easy for a minority of carriers to pass through the PN junction in reverse deflection, so these carriers-electrons can easily move upward through the junction region of the reverse state to form a collector current IC. Thus, the formation of the collector current is not necessarily dependent on the high potential of the collector. The size of the collector current depends on the emission and injection of the carrier to the base region, depending on the extent of the emission and injection, the carrier's emission injection degree is almost nothing to do with the collector potential of Gaudi. This is a natural way of explaining why the collector current IC is independent of the size of the collector potential VC when the transistor is amplified. The function of VC,VC under the amplification state IC is to maintain the inverse state of the collector Junction, in order to meet the external electrical conditions required in the transistor amplification state.

The essence of the IC is the "little sub" current, which is an artificially controllable collector "drain" current that is realized by electronic injection, so it can be easily reversed through the collector junction.

Transistor saturation, the collector potential is very low even near or slightly lower than the base potential, the junction is 0 offset, but there will still be a large set of junction reverse IC generation.

Analysis of transistor working principle