The Operational Transconductance Amplifier (OTA),which implies differential input voltage to single-ended current as the output. The aim of market to design low cost at low supply voltage to get high frequency application like radio, micro-wave, front-ended amplifier etc.This book mainly focused on the design and implementation of conventional Operational Transconductance Amplifier (OTA) and two-stage Operational Transconductance Amplifier by using various low power techniques.