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bipolar transistors

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Bipolar Transistors
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Bipolar Transistors

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Figure 22-1. NPN transistor.

Transistor Construction

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Figure 22-2. PNP transistor.

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Transistor Types and PackagingTransistor classifications

According to type NPN or PNP

According to material used Germanium or silicon

According to major use High or low power, switching, or high frequency

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Transistor Types and Packaging(cont’d.)

Transistor identificationPrefix of 2N followed by up to four digits

Transistor packageProtects transistorProvides means of electrical connectionServes as a heat sinkIdentified with letter TO (transistor outline)

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Transistor Types and Packaging(cont’d.)

Figure 22-3. Various transistor packages.

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Transistor Types and Packaging(cont’d.)

Figure 22-4. Typical transistor packages.

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Figure 22-5. Properly biased NPN transistor.

Basic Transistor Operation

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Figure 22-6. Properly biased PNP transistor.

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Figure 22-7. Resistance measurements of transistor junctions.

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Figure 22-8. Transistor tester.

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Transistor Substitution

Figure 22-9. How to remember the polarity of the collector voltage.

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SummaryA transistor is a three-layer device used to

amplify and switch power and voltageA transistor is classified according to type,

material used, and major useIn a properly biased transistor, the emitter-

base junction is forward biased and the collector-base junction is reverse biased

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Summary (cont’d.)PNP transistor bias sources are the reverse

of NPN bias sourcesWhen a transistor is tested with an

ohmmeter, each junction exhibits a low resistance when it is forward biased and a high resistance when it is reverse biased

Transistor testers are available for testing transistors in and out of circuit