A switched-capacitor band-pass biquad filter using a simple quasi-unity gain amplifier

Abstract

This paper presents a switched-capacitor (SC) band-pass biquad using a simple quasi-unity gain amplifier. In sub-nanometer CMOS technologies the intrinsic gain of the transistors is low; this increases the difficulty of designing high gain amplifiers. The proposed SC filter is based on the Sallen-Key biquad and it requires only a simple low gain amplifier. A differential filter circuit, including a suitable amplifier based on a fullydifferential voltage-combiner is presented and analyzed. The correct functionality of this circuit is validated through electrical simulations of a second-order band-pass filter. These simulations show that, for a clock frequency of 100 MHz, the frequency response of the circuit is similar to the corresponding prototype filter.