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Attenuation-Predistortion Linearization of CMOS OTAs With Digital Correction of Process Variations in OTA-C Filter Applications

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4 Author(s)
Mobarak, M. ; Dept. of Electr. & Comput. Eng., Texas A&M Univ., College Station, TX, USA ; Onabajo, M. ; Silva-Martinez, J. ; Sanchez-Sinencio, E.

An architectural attenuation-predistortion linearization scheme for a wide range of operational transconductance amplifiers (OTAs) is proposed and demonstrated with a transconductance-capacitor (G<sub>m</sub>-C) filter. The linearization technique utilizes two matched OTAs to cancel output harmonics, creating a robust architecture. Compensation for process variations and frequency-dependent distortion based on Volterra series analysis is achieved by employing a delay equalization scheme with on-chip programmable resistors. An OTA design with the proposed broadband linearization method has third-order inter-modulation (IM3) distortion better than -74 dB up to 350 MHz with 0.2V¿¿ input, 70 dB signal-to-noise ratio (SNR) in 1 MHz bandwidth, and 5.2 mW power consumption. The distortion-cancellation technique enables an IM3 improvement of up to 22 dB compared to a commensurate OTA without linearization. A proof-of-concept low-pass filter with the linearized OTAs has a measured IM3 < - 70 dB and 54.5 dB dynamic range over its 195 MHz bandwidth. The standalone OTAs and the filter were fabricated on a 0.13 ¿m CMOS test chip with 1.2 V supply.

Published in:

Solid-State Circuits, IEEE Journal of  (Volume:45 ,  Issue: 2 )