REALIZATION OF OTA BASED SHADOW FILTERS

Abstract

Shadow filter is a second order filter in which an external amplifier is placed in the feedback path and the characteristics of such a filter are tuned by adjusting the gain (G) of the external amplifier. New voltage-mode electronically tunable band pass, notch, high pass and low pass shadow filters are proposed. The filters are built around the operational transconductance amplifier (OTA). OTA provides an electronic tuning capability of its transconductance gain by adjusting its bias current or voltage and is implemented by using the CMOS technology. The circuits implemented by using the OTA does not .require a resistor which is ideal .for any of the integrated circuit. Implementation. In every case one or more than one parameters of the filters can be electronically controlled by adjusting the gain of an external amplifier built around the operational transconductance amplifier. The proposed circuit has utilized the MISO configuration, avoiding the external summing amplifier for implementing the shadow filter. For realizing the filter functions, there is no need of the component-matching conditions. The proposed shadow filter is simulated using SPICE simulator with 0.35 µm CMOS process from TSMC to confirm the presented theory.