Teach Yourself Electricity and Electronics, Sixth Edition, 6th Edition

21

CHAPTER

Bipolar Transistors

THE WORD TRANSISTOR IS A CONTRACTION OF “CURRENT-TRANSFERRING RESISTOR.” A BIPOLAR TRANsistor has two P-N junctions. Two configurations exist for bipolar transistors: a P type layer between two N type layers (called NPN), or an N type layer between two P type layers (called PNP).

NPN versus PNP

Figure 21-1A is a simplified drawing of an NPN bipolar transistor, and Fig. 21-1B shows the symbol that engineers use for it in schematic diagrams. The P type, or center, layer constitutes the base. One of the N type semiconductor layers forms the emitter, and the other N type layer forms the collector. We label the base, the emitter, and the collector B, E, and C, respectively.

21-1   At A, a simplified structural drawing ...