CHAPTER 16 ■ TRANSISTOR SWITCHESI can’t think of a more concrete example to demonstrate that PNP and NPN transistors are generally
identical in function except the negative and positive are reversed.
Pay attention to the flat side of the NPN transistor (Q1). You may mistakenly want to install it with the
label facing you. Also, as with the PNP transistor test circuit, you can follow the same steps with the NPN
transistor test circuit to determine the transistor’s emitter, base, collector, and gain.
Brightness Comparator Circuit with Transistors
Recall the brightness comparator circuit from the prior chapter. The diagram shown in Figure 16-9 is very
similar to that earlier circuit, except that transistors now switch the LEDs.
Figure 16-8. NPN transistor test circuit built on a solderless breadboard