The filter shown in the figure is suggested by National Semiconductor having a cutoff frequency of 100Hz determined by the values of the capacitors and resistors used. The filter is first order with 6 dB per octave and the operational amplifier is the LM102. Other operational amplifiers can be used respecting their characteristics, mainly of maximum frequency of operation. The power supply must be symmetrical and in the pass band the gain of the circuit is unitary.
