A 10th order SC band-pass filter and its smooth filter design
This paper designs a 10th order switched-capacitor (SC) band-pass filter and its 6th 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 [1], 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.