In this chapter, we’re going to deal with discrete transistors: the kind packaged one at a time with three leads out the bottom. This isn’t just an academic exercise. If you need to shift more current or voltage than the pins on your Cestino can handle, you’ll probably reach for a transistor, particularly a Darlington transistor. (More on these in a bit.) Whereas the output pins on the Cestino can source or sink no more than 40mA at five volts, a TIP120 Darlington with a proper heat sink can sink 5 amps (5000mA) at up to 60 volts, and can be easily driven by one of the Cestino’s output pins.