What is diode limiters?

Answer 1

AC, or alternating current, is when the current's voltage varies as a sine wave, say alternating from 120 V to -120 V with a period typically on the order of microseconds. Some devices, however, have a maximum current, typically much less than 120 V. In this case, a "diode limiter" is used. The diode limiter is essentially a circuit that does nothing when the voltage is between 0 V and whatever the maximum specified voltage is, but "clips" or "limits the voltage above that. So after, say, 20 V, the sine wave flattens out and is a straight line until it starts to decrease down to -20 V, at which point it becomes a flat line again. Such circuits are made by diodes (hence the name), which are primarily used for turning AC current into DC current.

Answer 2

A peak-limiting circuit employing a diode that becomes conductive when signal peaks exceed a predetermined value.