The function of the clipper is to ensure that the input waveform never exceeds a certain peak value. This may be a protective function, that is, a large signal might damage a following circuit, but it may be used for other reasons, for example, ensuring that signal overage is never reached. Clipping circuits do not have to be symmetrical. In other words, the positive and negative limits do not have to have the same magnitude. While clippers can be designed using Zener diodes, the biased clipper offers the advantage of infinite variability of the limit point. In contrast, Zener based clippers are limited by the available standard zener potentials and cannot be set to new values without replacement of the Zeners.
Clamper circuits are designed to provide a DC level shift. Typically this means shifting a waveform vertically so that the entire waveform is either positive or negative with one peak now residing at zero.