![]() Once in this region they are pulled through the reverse-biased BC junction by the electric field set up by the force of attraction between the positive and negativeġ2 4-2 Basic Transistor Operation (cont.) ![]() Once in this region they are pulled through the reverse-biased BC junction by the electric field set up by the force of attraction between the positive and negativeġ1 4-2 Basic Transistor Operation (cont.) Most of electrons from the emitter diffuse into the BC depletion region. Thus only a small percentage of all the electrons flowing through the BE junction can combine with the available holes in the base.ġ0 4-2 Basic Transistor Operation (cont.)Ī few recombined electrons flow out of the base lead as valence electrons, forming the small base electron current. The base region is lightly doped and very thin so that it has a very limited number of holes. The heavily doped n-type emitter region is teeming with conduction-band (free ) electrons that easily diffuse through BE junction into the p-type base region where they become minority carriers. The forward bias from base to emitter narrow the BE depletion region, and the reverse bias from base to collector widens the BC depletion region. The figure shown the proper bias arrangement for both npn and pnp transistor for active operation as an amplifier. ![]() To operate the transistor properly, the two pn junction must be correctly biased with external dc voltages. The base region is lightly doped and very thin compared to the heavily doped emitter and the moderately doped collector region The pn junction joining the base region and the emitter region is called the base-emiter junction The pn junction joining the base region and the collector region is call base-collector junction ![]() The BJT have 2 types: Two n region separate by a p region – called npn Two p region separated by a n region – called pnp The three region are called emitter (E),base (B) and collector (C) The BJT is constructed with three doped semiconductor regions separated by two pn junctions. Chapter 4 Bipolar Junction Transistors (BJTs)Ģ Objectives Describe the basic structure of the bipolar junction transistor (BJT) Explain and analyze basic transistor bias and operation Discuss the parameters and characteristics of a transistor and how they apply to transistor circuits
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