![]() So we have a strong current flow from the emitter to the collector oppositely directed to the electron flow. The rest of the of electrons go to the collector and collect there. The electrons emitted by the emitter, passing through the base, experience a small recombination. ![]() The base here should be much thinner than the emitter. ![]() Here the flow of electrons is heavier, because the layer is more heavily doped. The electrons will flow from the emitter to the base, and the holes will flow from base to an emitter. Let’s consider a situation where for transistor – the base-emitter junction operates like a classical junction, or diode, being forward-biased. The transistor’s work may be understood easily if you recon previous section on how a pn-junction works. The schemes of pnp (a) and npn (b) transistors Schematically these two transistors are depicted below. These BJTs are called pnp and npn transistors respectively. it can be formed by the -layer situated between p- and p + -layers, or p-layer between n– and n +-layer. The BJT is made by combined semiconductor materials with different doping levels, i.e. The two-terminal p-n junction is the basis for a great variety of more complex semiconductor devices, and the bipolar junction transistor is one of them. Schemes for current-controlled and voltage-controlled switches based on the transistor’s operation Bipolar junction transistor In the non-linear mode transistors act as current-controlled and voltage-controlled switches (below). The operating modes of a transistor as a linear amplifier The bipolar junction transistor (BJT) plays the role of the current-controlled amplifier, the field-effect transistor (FET) plays role of the voltage-controlled amplifier. The current and voltage sources exist in order to generate the current or voltage output level proportional to the input with the certain constant, which is called the gain of the transistor. There is four possible modes of transistor operation as a linear amplifier – current-controlled current source, voltage-controlled current source, current-controlled voltage source and voltage-controlled voltage source. The operation of a transistor as a linear amplifier is schematically described below. A transistor is a three-terminal semiconductor device that can perform amplification and switching functions.
0 Comments
Leave a Reply. |