Low power architecture and circuit techniques for high boost wideband Gm-C filters

摘要

With the current trend towards integration and higher data rates, read channeldesign needs to incorporate significant boost for a wider signal bandwidth. Thisdissertation explores the analog design problems associated with design of such'Equalizing Filter' (boost filter) for read channel applications.Specifically, a 330MHz, 5th order Gm-C continuous time lowpass filter with24dB boost is designed. Existing architectures are found to be unsuitable for low power,wideband and high boost operation. The proposed solution realizes boosting zeros byefficiently combining available transfer functions associated with all nodes of cascadedbiquad cells. Further, circuit techniques suitable for high frequency filter design areelaborated such as: application of the Gilbert cell as a variable transconductor and a newCommon-Mode-Feedback (CMFB) error amplifier that improves common modeaccuracy without compromising on bandwidth or circuit complexity. A prototype isfabricated in a standard 0.35mm CMOS process. Experimental results show -41dB ofIM3 for 250mV peak to peak swing with 8.6mW/pole of power dissipation.