Transistor Tutorial history sample circuits


Posted on Feb 5, 2014

The bipolar junction transistor is still one of the cornerstone`s of modern solid-state electronics. Learn (or review) the basics of this important active device. The Bipolar Junction Transistor (BJT) triggered the revolution in modern solid-state electronics in the 1960`s. Although the discrete small-signal BJT has since yielded to the integrated


Transistor Tutorial history sample circuits
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circuit (IC) in economic importance, it lives on in the form of discrete linear and switching power transistors as well as radio-frequency transistors into the microwave region. The principles behind the operation of the BJT are important to the understanding of many of today`s most popular linear and digital integrated circuits. Moreover, the transistor families-TTL, Schottky TTL, and emitter-couple logic (ECL) are BJT`s. A BJT is a three-terminal (base, emitter, and collector) device. There are two types: NPN and PNP. Today both are typically made by the double-diffusion process that involves the deposition of two additional layers of doped silicon on a doped silicon wafer. Figure 1-a shows the cross section of an NPN BJT. Its base and emitter terminals are metal depositions on top of the silicon wafer, and its collector is the metalized lower surface of the wafer. Figure 2-a shows the cross section of a PNP BJT. It is similar to the NPN BJT, except that the N- and P-type materials have changed places. Figure 1-b and 2-b are the schematic symbols for the NPN and PNP transistors, respectively. Notice that they are the same except for the direction of the arrowhead within the symbol at the emitter terminal. This difference will be explained shortly. The term bipolar means that the BJT`s operation depends on the movement of two different carriers: electrons and holes. In NPN BJT`s the electron is the majority carrier and...




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