Electronically Tunable Voltage-Mode All-Pass Filter Using Simple CMOS OTAs

A new high input impedance electronically tunable voltage-mode first-order all-pass filter using three simple CMOS operational transconductance amplifiers (OTAs) and one grounded capacitor is presented. The corner frequency can be controlled electronically by adjusting the bias currents of OTAs. Critical component matching conditions are not required in the design. The use of a grounded capacitor and without resistor makes the proposed circuits ideal for integrated circuit implementation. The characteristics of the proposed circuit are simulated using PSPICE to verify the theory.