Simple realization of a third order Butterworth filter with MOS-only technique

Recently, many active filter circuits that use only MOS transistors were presented in the literature. In these circuits, instead of passive resistors, transconductances of MOSFETs operating in saturation region are used. Moreover, their parasitic gate to source capacitances are employed instead of passive capacitors. These circuits provide circuit implementation with fewer transistors and eliminate the need for external passive elements. In this study, a MOS-only third order Butterworth filter for high frequency applications has been proposed. The circuit leads to a compact circuit having fewer number of transistors compared to classical active block-based analog counterparts. Simulation results agree well with the theoretical study.