Seventh-order elliptic video filter with 0.1 dB pass band ripple employing CMOS CDTAs

In this paper, a CMOS realization of the current differencing transconductance amplifier (CDTA) is given, which is a newly reported active building block for current-mode signal processing. Current differencing stage of the CDTA element is realized using a differential current-controlled current source and in the output stage, floating current sources are used to convert intermediate voltage of z terminal to output currents. Due to the compactness of the circuit, it is capable of high-frequency operation and suitable for video signal-processing applications. The CDTA element is used in a current-mode anti-aliasing video filter, which is designed using operational simulation of a seventh-order passive elliptic filter, so the resulting active filter has the low sensitivity feature of its passive counterpart. The filter has 0.1 dB maximum pass band ripple as imposed by ITU video anti-aliasing filter standard. SPICE-simulation results of both the CDTA element and the seventh-order elliptic filter are given. Simulation results are found in close agreement with theoretical results.