High-pass Filters

High-Pass Filters

Ideally, a high-pass filter allows through it all signal components above a certain (cutoff) frequency and blocks off all signal components below that frequency. A single-pole high pass filter. As for the low-pass filter that was discussed earlier, the passive filter stage and the active filter stage have identical transfer functions. The active filter is desired, however, because of its many advantages, including negligible loading error due to high input impedance and low output impedance of the op amp voltage follower that is present in this circuit.

Filter equation is obtained by considering current balance noting that the output is in open circuit (zero load current). Accordingly,

A single-pole high-pass filter: (a) A passive filter stage, (b) An active filter stage, (c) Frequency response

characteristic.