![]() ![]() ![]() Therefore, holes are attracted from the emitter into the base region. In the case of the pnp transistor, electrons are injected into the n-doped base region. Suppose that the collector potential is lower than the emitter potential and that the base potential is roughly 0.7 V lower than the emitter potential. Most of the remaining electrons are swept across the very thin base region and contribute to the collector current. ![]() Since the emitter region is very heavily doped, many more electrons enter the base region than holes, and some of the electrons recombine with holes. As a result, these holes attract electrons from the emitter into the base region across the forward-biased base-emitter junction. When the base-emitter junction is forward-biased, a small current flows into the base, injecting holes into the p-doped base region. In other words, the base-emitter junction is forward-biased whereas the base-collector junction is reverse-biased. Let’s consider the npn transistor where the collector potential is higher than the emitter potential and the base potential is roughly 0.7 V higher than the emitter potential. When each terminal is at the specified voltage, the collector draws a current that is h FE times higher than the current applied to the base. In this way, a bipolar transistor is formed by two back-to-back diodes. To obtain a high current gain, the emitter region is orders of magnitude more heavily doped than the base region. The base region shares two pn junctions, each with collector and emitter. A bipolar transistor (bipolar junction transistor: BJT) consists of the collector, base, and emitter regions, with the very thin base region located between the collector and emitter regions. ![]()
0 Comments
Leave a Reply. |