Amplitude controllable current-mode first order allpass filter including minimum component count circuits

Abstract

This paper presents a current-mode first order allpass filter based on current follower cascaded transconductance (CFCTA). The phase shifted angle and amplitude of output currents can be electronically and independently tuned via the bias current. The proposed circuit uses only one CFCTA and one grounded capacitor and one electronic resistor, which is definitely suitable to further develop into an integrated circuit. It can provide both non-inverting and inverting output currents. Moreover, the circuit possesses low input and high output impedance, providing easy cascading in current-mode circuit. The PSPICE simulation results based on 0.25μm TSMC CMOS parameters are included, verifying the key characteristics of the presented filter. The given results agree well with the theoretical presumptions. The power consumption is about 5.5mW.