untitled

Transistors come in

NPN (negative/positive/negative):You turn on NPN transistors by apply-

ing positive voltage; they start to turn on when you apply about 0.7 volts.

We use NPN transistors throughout this book because it’s more straight-

forward to apply a positive voltage to get things working.

PNP (positive/negative/positive):You turn off PNP transistors by apply-

ing positive voltage; they turn on when you apply negative voltages or

voltages near ground.

Transistors have three leads: the emitter, base, and collector. In Chapter 4,

we show you how to read schematics so you can figure out where to connect

each pin. For each transistor you use, check the datasheet (which contains a

drawing, called a pinout) to determine which pin is which.

ICs ...........................................................................................................

Integrated circuits — commonly known as ICs— are like social directors

for components: They gather lots of other components in a single location

TO-92 TO-39 T0-220

Figure 3-5:

Common

transistor

packages.

42 Part I: Project Prep