Ch 3a 2006

Ch 3a 2006 - Ch. 3.0 The Bipolar Junction Transistor In the...

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The Bipolar Junction Transistor In the last chapter, we saw that the rectifying current voltage characteristics of the diode are useful in electronic switching and wave shaping circuits. However, diodes are not capable of amplifying currents or voltages. One of the electronic devices that is capable of current and voltage amplification, or gain, in conjunction with other circuit elements, is the transistor, which is a three-terminal device. The development of the silicon transistor by Bardeen, Brattain. and Schockley at Bell Telephone Laboratories in the late 1940s started the first electronics revolution of the 1950s and 1960s. This invention led to the development of the first integrated circuit in 1958 and to the operational transistor amplifier (op-amp), which is one of the most widely used electronic circuits. The bipolar transistor, which is introduced in this chapter, is the first of two major types of transistors. The second type of transistor, the field-effect transistor FET). is introduced in Chapter 5 and has led to the second electronics revolution in the 1970s and 1980s. These two device types are the basis of modern day microelectronics. Each device type is equally important and each has particular advantages for specific applications. We begin this chapter with a look at the physical structure and operation of the bipolar transistor. The chapter deals mainly with the transistor characteristics and with the dc analysis and design of bipolar circuits. We continue to use the piecewise linear approximation techniques, developed for the diode, in the bipolar transistor calculations. We discuss how the transistor can be used in switch, digital, and linear amplifier applications. Much of the material in this chapter may appear to be skewed toward discrete transistor biasing. However, the principal goal of the chapter is to ensure that readers become familiar with transistor characteristics and are able to quickly analyze and design the dc response of bipolar transistor circuits. Integrated circuit biasing is discussed toward the end of the chapter and is emphasized to a greater extent in the later chapters. 3.1 BASIC BIPOLAR JUNCTION TRANSISTOR The bipolar junction transistor (BJT) has three separately doped regions and contains two pn junctions. A single pn junction has two modes of operation; forward bias and reverse bias. The bipolar transistor, with two pn junctions therefore has four possible modes of operation, depending on the bias condition of each pn junction, which is one reason for the versatility of the device. With three separately doped regions, the bipolar transistor is a three-terminal device. The basic transistor principle is that the voltage between two terminals controls the current through the third terminal. EE 329
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This note was uploaded on 09/10/2011 for the course EE 3114 taught by Professor Moon during the Spring '10 term at NYU Poly.

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Ch 3a 2006 - Ch. 3.0 The Bipolar Junction Transistor In the...

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