Frequency compensation in a two-integrator loop Gm-C biquad when realized with single stage OTAs

Abstract

The paper considers the design of a two-integrator loop Gm-C second order filter, realized by single stage operational transconductance amplifiers (OTA). Two major problems are discussed: equalizing the maxima of OTA input voltages and unfavorable effect of OTA input capacitances. It is shown OTA input capacitances cause increasing of pole Q-factor and may turn the circuit to unstable. A method for avoiding of this problem is proposed, which could be applied for the other circuits of this class.