Design of a Third Order Butterworth Gm-C Filter for EEG Signal Detection Application

This paper presents the design of a fully differential low pass G
_m
-C filter including the preamplifier circuit as an input stage. The design is targeted for a biomedical application such as electroencephalogram signal detection. The complete circuit including supporting circuitry has been designed and implemented in a standard 180 nm CMOS technology with the supply voltage of 1.8 V. The post-layout simulation results show 21.8 dB closed loop gain, 206 Hz 3-dB bandwidth, and 689 nW power consumption. The designed filter gives effectively third order butterworth response including the preamplier circuit. The filter shows a transconductance of 2.8 nS at 200 Hz frequency. The filter shows satisfactory performance from -20 °C to 80 °C with varying process corners. The statistical mismatch analysis shows 724 ndB standard deviation of gain from the mean value of 21.8 dB. Input referred noise (IRN) shows 94.6 aV/√Hz standard deviation from the mean value of 81.7 μV/√Hz.