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.
 P. Pandey, J. Silva-Martinez, and A. Liu Xuemei, “CMOS 140-mW fourth-order continuous-time low-pass filter stabilized with a class AB common-mode feedback operating at 550 MHz”, IEEE Tran. Circ. Syst. I: Reg. Papers 56, 811-820 (2006).
 V. Saari, M. Kaltiokallio, S. Lindfors, J. Ryynanen, and K.A.I. Halonen, “A 240-MHz low-pass filter with variable gain in 65-nm CMOS for a UWB radio receiver”, Tran. Circ. Syst. I: Reg. Papers 56, 1488-1499 (2009).
 Afzali-Kusha, M. Nagata, N.K. Verghese, and D.J. Allstot, “Substrate noise coupling in SoC design: modeling, avoidance, and validation”, Proc. IEEE 94, 2109-2138 (2006).
 E. Charbon, R. Gharpurey, P. Miliozzi, R.G. Meyer, and A. Sangiovanni-Vincentelli, Substrate Noise: Analysis and Optimizationfor IC Design, KAP, Boston, 2003.
 P.E. Allen and D.R. Holberg, CMOS Analog Circuit Design, Oxford University Press, Oxford, 2002.
 G. Giustolisi, G. Palmisano, and G. Palumbo, “CMRR frequency response of CMOS operational transconductance amplifiers”, IEEE Tran. Instrument. Measurement 49, 137-143 (2000).
 C. Sripaipa and W.H. Holmes, “Achieving wide-band commonmode rejection in differential amplifiers”, Proc. IEEE 58, 600-602 (1970).
 A.A. Ciubotaru, “Technique for improving high-frequency CMRR of emitter-coupled differential pairs”, IET ElectronicsLetters 38, 943-944 (2002).
 F. You, S.H.K. Embabi, and E. Sanchez-Sinencio, “On the common mode rejection ratio in low voltage operational amplifiers with complementary N-P input pairs”, IEEE Tran. Circ. Syst. II: Analog Digital Signal Proc. 44, 678-683 (1997).
 P.S. Crovetti and F. Friori, “Finite Common-mode rejection in fully differential operational amplifiers”, IET Electronics Letters 42, 615-617 (2006).
 S. Szczepanski, J. Jakusz, and R. Schaumann, “A linear fully balanced CMOS OTA for VHF filtering applications”, IEEETran. Circ. Syst. Part II: Analog Digital Signal Proc. 44, 174-187 (1997).
 S. Koziel and S. Szczepanski, “Dynamic range comparison of voltage-mode and current-mode state-space Gm-C biquad filters in reciprocal structures”, IEEE Tran. Circ. Syst. I: RegularPapers 50, 1245-1255 (2003).
 J.F. Fernandez-Bootello, M. Delgado-Restituto, and A. Rodrıguez- Vazquez, “IC-constrained optimization of continuoustime Gm-C filters”, Int. J. Circ. Theory Applic. 40, 127-143 (2012).
 A. Lewinski and J. Silva-Martinez, “OTA linearity enhancement technique for high frequency applications with IM3 below −65 dB”, IEEE Tran. Circ. Syst. Part II: Express Briefs 51, 542-548 (2004).
 R. Schaumann and Mac E. Van Valkenburg, Design of AnalogFilters, Oxford University Press, Oxford, 2001.
 A. Otin, S. Celma, and C. Aldea, “Continuous-time filter featuring Q and frequency on-chip automatic tuning”, Int. J. Circ. Theory and Appl. 37, 221-242 (2009).