As shown in FIG staggering low frequency active filter circuit. This is a fourth-order Butterworth low-pass active filters for filtered VLF random pulse noise voltage DC level
signal on its cut-off frequency (-3dB) about 8Hz, at 18Hz at 20dB gain reduction. Intrinsic attenuation in the passband of 0.467. Input resistance is approximately 40k. Filter network using a number of resistors are metal film precision resistor in series. If one 1 F capacitor to achieve a considerable accuracy, the cutoff frequency fc close to the theoretical value.