RC filters are designed to modify, reshape or reject all unwanted frequencies of an electrical signal and accept or pass only those signals wanted by the circuit’s designer. In other words they “filter-out” unwanted signals. Filters are named according to the frequency range of signals that they allow to pass through them, while blocking or “attenuating” the rest. The point at which a filter passes or blocks a signal is called the corner frequency, (fc).
Ideal Filter Response
The pass band allows signals to freely pass unattenuated, while the stop band blocks all signals.