A 10th order SC band-pass filter and its smooth filter design

This paper designs a 10^th order switched-capacitor (SC) band-pass filter and its 6^th order active-RC low-pass smooth filter. The center frequency and -3dB pass bandwidth of the SC filter are respectively 50kHz and 10kHz. The filters are used in a low-frequency communication system. At low frequency, the MOSFETs have large flicker noise. This paper designs an optimized low noise full differential op amp with rail-to-rail output. The filters are synthesized using an improved design approach, which is based on the active ladder synthesis method. With this approach, the precisions of the frequency response of the filters are improved and the dynamic ranges are increased. Post-layout simulation results of the total filters are ±0.5% of center frequency error, 0.4dB of pass-band ripple, below -83.5dB of stop-band rejection where stop-band width is 100kHz and 78.8dB of dynamic range.