Implementation of active filter using OTA

Implementation of active filters using OTA-C circuits

Winter Training Report

CONTENTS Title Page no.
1) Introduction to OTAs 2
2) Advantages of OTAs 3
3) First Order Filter using OTAs 4
4) Second Order Filter using OTAs 5
5) Second Order universal filter 8
6) Nth order filter using OTA 11
7) Model analysis of second order filter 11 from the general structure

Introduction to
Operational Transconductance Amplifier
The operational transconductance amplifier (OTA) is an amplifier whose differential input voltage produces an output current. Thus, it is a voltage controlled current source (VCCS). There is usually an additional input for a current to control the amplifier's transconductance. The OTA is similar to a standard operational amplifier in that it has a high impedance output stage and that it may be used with negative. For an OTA
Iout=gm (VIN2-VIN1)

where gm is the transconductance or the gain of the OTA

Internal Circuit of an OTA

Symbolic notation and equivalent circuit of an OTA

Advantages of OTAs over operational amplifiers
1) There is no need for negative feedback in case of OTAs as compared to opamp which need negative feedback to reduce the sensitivity of the op amp to device parameters. The transconductance can simply be taken as a circuit element during design.

2) Unlike op amps in which a large number of matched resistors are needed for realisation of active circuits many of the basic OTA based structures use only OTAs and capacitors and, hence, are attractive for integration. Component count of