Technique to improve CMRR at high frequencies in CMOS OTA-C filters

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Abstract

In this paper a technique to improve the common-mode rejection ratio (CMRR) at high frequencies in the OTA-C filters is proposed. The technique is applicable to most OTA-C filters using CMOS operational transconductance amplifiers (OTA) based on differential pairs. The presented analysis shows that a significant broadening of CMRR bandwidth can be achieved by using a differential pair with the bodies of transistors connected to AC ground, instead of using a pair with the bodies connected to the sources. The key advantages of the technique are: no increase in power consumption (except for an optional tuning circuit), a small increase of a chip area, a slight modification of the original filter. The simulation results for exemplary OTAs and a low-pass filter, designed in a 0.35 μm CMOS process, show the possibility of broadening the CMRR bandwidth several times.

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IMPACT FACTOR 2016: 1.156
5-year IMPACT FACTOR: 1.238

CiteScore 2016: 1.50

SCImago Journal Rank (SJR) 2016: 0.457
Source Normalized Impact per Paper (SNIP) 2016: 1.239

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