A 40MHz 4th-order active-UGB-RC filter using VCO-based amplifiers with zero compensation

Abstract

This paper describes a 4th-order active-UGB-RC filter using VCO-based amplifiers with zero compensation. The VCO-based amplifier intrinsically has a huge DC gain without the associated stability penalties of conventional multi-stage amplifiers such as reducing unity-gain bandwidth or requiring large area by compensation schemes. By using the large gain of the amplifier, the filter achieves small area and good linearity performance for a signal bandwidth of 40MHz. The filter prototype in a 55nm CMOS process has an active area of 0.07mm2 and a power consumption of 7.8mW at 1.2V. The measured in-band IIP3 and out-of-band IIP3 are 27.3dBm and 22.5dBm respectively.