SCTF loop for noise reduction in Autozero amplifiers

The use of a lowpass switched continuous time filter (SCTF) in the noise cancellation loop of an Autozero amplifier to reduce the white noise aliasing effect at low frequencies is presented. The SCTF limits only the bandwidth of the sampled noise, not the bandwidth of the amplifier. Time domain simulations showing the effect of the SCTF-Autozero on both flicker and white noise are presented, as well as a designed low-noise electroencephalography (EEG) amplifier (DC - 150 Hz) that takes advantage of the proposed technique for a 40- reduction of its input rms noise voltage.