A Subthreshold Buffer-Based Biquadratic Cell and Its Application to Biopotential Filter Design

作者：Thanapitak Surachoke; Sawigun Chutham^*

来源：IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS, 2018, 65(9): 2774-2783.

DOI：10.1109/TCSI.2018.2808361

• Analog filter
• biomedical filter
• biopotential acquisition
• buffer
• CMOS
• ECG
• (gm)-C
• lowpass filter
• low voltage
• nanopower
• voltage follower

This paper develops a compact power-efficient CMOS buffer to operate as a nanopower lowpass biquadratic cell. Unlike other recently reported CMOS biquads with passband gains that are attenuated by the bulk effect, this biquad attains a near 0-dB passband gain without gain compensation. It acquires the same levels of input and output common-mode voltages making it useful for cascade realization of a higher order lowpass filter. To demonstrate the potential application of the proposed biquad, a fourth-order lowpass filter was designed based on the proposed biquad circuit and fabricated in the 0.35-mu m CMOS process to serve electrocardiography readout systems. Measurement results show that the filter consumes 4.26-nW static power from a 0.9-V supply providing a 100-Hz cutoff frequency. The prototype chip occupies a silicon area of 0.11 mm(2) and contributes an input-referred noise of 80.5 mu V-rms. For a 60-Hz input frequency associated with -50-dB third-order harmonic distortion, a dynamic range of 48.2 dB is achieved. The lowest power supply rejection ratio of 40 dB was obtained at 100 Hz. Compared with the previous state-of-the-art designs in the category of nanopower filters, the proposed filter consumes the least power from the lowest supply voltage.

• 出版日期2018-9