Complete Electronics Self-Teaching Guide with Projects

Understanding Transistors

1 The diagrams in Figure 3.1 show some common transistor cases (also called packages). The cases protect the semiconductor chip on which the transistor is built and provide leads that can be used to connect it to other components. For each transistor, the diagrams show the lead designations and how to identify them based on the package design.

Transistors can be soldered directly into a circuit, inserted into sockets, or inserted into breadboards. When soldering, you must take great care because transistors can be destroyed if overheated. A heat sink clipped to the transistor leads between the solder joint and the transistor case can reduce the possibility of overheating. If you use a socket, you can avoid exposing the transistor to heat by soldering the connections to the socket before inserting the transistor.

Figure 3.1

Questions

A. How many leads are there on most transistors? _____

B. Where there are only two leads, what takes the place of the third lead? _____

C. What are the three leads or connections called? _____

D. Why should you take care when soldering transistors into a circuit? _____

Answers

A. Three.

B. The case can be used instead, as indicated in the diagram on the right side of Figure 3.1. (This type of case is used for power transistors.)

C. Emitter, base, and collector.

D. Excessive heat can damage a transistor.