Gm-C Biquad Filter for Low-Signal Sensor Applications

R. Arya (UNINOVA, Portugal), J. Oliveira (UNINOVA and Univ. Nova Lisboa, Portugal)

This paper presents a circuit architecture for gm-C biquad filter, suitable for low frequency, low amplitude signals. The OTA is designed using a current division technique in order to achieve low transconductance value. A second order biquad based on Two-Thomas biquad design is implemented using the OTA. The filter operates in weak inversion with a supply of 0.9V, has a cutoff frequency of 48Hz, and power consumption about 800nW. The integrated Noise of filter is 17.4 μVrms, dynamic range of 44dB, and it shows —40dB THD for 3.8mV Input peak amplitude. Monte-carlo analysis gives a mean cutoff frequency of 47.84Hz with 6.89% standard deviation.