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Fully Differential Band-pass Filter for Biosignals Based on a DFVF and High CMRR

This paper presents a study to build firstly a pair of low effective transconductance OTAs, and secondly to choose the better OTA for designing a band-pass amplifier suitable to process biosignals, where it is desirable to obtain high CMRR. From this study one of the OTAs reaches a CMRR of 87dB when a ±0.5V bias is used, while the required cut-off frequencies (0.5Hz and 10.0kHz) are well achieved. The effective transconductance of the OTA at room temperature is gm=695nS. In order to satisfy the required high-pass cut-off frequency, a pole based on a pseudoresistor was designed. The effective resistance based on a pseudoresistors is 1.53TΩ. Both Corners and Monte Carlo simulations were carried out to verify the whole pass-band filter performance. Designed in a 130nm standard CMOS technology, the best OTA achieves up to 113dB of CMRR when a bias voltage of ±0.6 V is used.