ANALOG FILTER DESIGN USING OTA

Abstract

The presence of several analog circuits with reduced components count, low power supply, better accuracy and fast speed is an extremely challenging task. Recently a number of papers have been published on analog filter design using CMOS technology. The least power consumption and highest fidelity is possible by using CMOS- Operational Transconductance Amplifier (OTA) instead of Op-amp. As a consequence, the CMOS based circuits approach has often been claimed to provide advantages of higher frequency range of operation, lower power consumption, higher slew rates, improved linearity, and better accuracy. This report describes the implementation of electronically tunable, analog filter based on Operational Transconductance Amplifier (OTA) using CMOS technology. The operational transconductance amplifier (OTA) is an amplifier whose differential input voltage produces an output current. Thus, it is a voltage controlled current source. There is usually an additional input for a current to control the amplifier's transcoductance. The transcoductance can be continuously controlled by an auxiliary DC current. It gives the possibility to control electronically the parameters of realized filters. In this work electronically tunable filter circuits such low pass, high pass, band pass, band stop in first order and second order has been implemented. A floating and grounded resistance using OTA has been implemented and the same is used in realizing the filters. In this work SPICE simulation of realization of OTA using CMOS technology, as the basic building block has been done and its DC characteristics are verified. The workability of electronically tunable, OTA based filters using CMOS technology has been confirmed by PSPICE Simulation and the results are compared with PSPICE simulation of the commercially available operational tranconductance amplifier LM13600/LM13700. Further hardware results are verified using the same commercial IC.