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 $\pmb{94.6}\mathbf{aV}/\sqrt{Hz}$ standard deviation from the mean value of $\pmb{81.7}u\mathbf{V}/\sqrt{Hz}$.

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