Second order low pass filter with voltage follower

Frequency response of second order low pass filter with voltage follower A series resistor from input signal followed by a shunt capacitor reduces the gain of high frequency inputs, and it's called a low pass filter (passes low frequencies). Second order filter has two such filters in series, so that gain reduces more quickly than in first order filter. The problem without the op-amp voltage follower is that the second filter is like a load to the first filter. With the voltage follower, the first filter sees an infinite impedance and the input impedance to the second filter is nearly zero from the op-amp output. The gain drops slightly before the desired 1kHz frequency, at about 40dB per decade.

published 9 years ago