Realization of current mode universal shadow filter

Abstract

In this paper, a current-mode universal shadow filter is proposed using a new variant of current differencing transconductance amplifier (CDTA), namely current controlled current differencing cascaded transconductance amplifier (CC-CDCTA) and two capacitors. It realizes three shadow filter functioning; low pass (LPS), high pass (HPS) and band pass (BPS). Furthermore, it is extended to a universal filter by adding one second generation current conveyor (CCII) and CC-CDCTA building blocks. The proposed configuration realizes all the standard responses of a universal shadow filter such as LPS, BPS, HPS, band-reject (BRS), and all pass (APS) simultaneously. It does not use any resistor. The presented shadow filter utilizes the LP and BP outputs of the basic filter in the feedback amplifier to obtain the desired universal shadow filter functionality. The pole frequency (ωos) and quality factor (Qos) of the shadow filter is electronically tunable using the gain of the feedback amplifiers. The ωos and Qos can also be tuned without disturbing each other. It is also found to be suitable for full cascadability. The validation is done using 180 nm technology in Cadence. Experimental verification has also been done using IC AD844, and CA3080 and found satisfactory results.