A state-variable filter with 2kHz-8kHz voltage-controlled center frequency based on ALD1106 quasi-floating-gate transistors

Abstract

A state variable filter with center frequency tuning capability is presented. Tuning is achieved by means of voltage-controlled integrators based on quasi-floating- gate transistors. An experimental prototype realized with three operational amplifiers, six capacitors, four resistors and four ALD1106 NMOS transistors presented tuning capability from 2kHz to 8kHz, with 0.28% of Total Harmonic Distortion in the low-pass response when an input of amplitude 0.2V and frequency 0.1kHz was employed