Circuit diagrams often show transistors in switching circuits. For an ideal NPN transistor, the switch-on voltage at the base is typically 0.6V (acceptable range is 0.6V to 0.8V).

In the early days, PNP bipolar transistors were common, but the bulk of circuits you see today use NPN transistors. As [Aaron Danner] points out, many people think PNP transistors are “backwa… ...