The Operational Transconductance amplifier are huge building hinders for various simple circuits and frameworks which were already executed by utilizing OPAMP. As of late, explore is continuing for actualizing OTA circuits which will be exceedingly direct, devours lesser power and work at bring down supply voltage. Past OTAs only occasionally worked more than 200MHz though, the higher recurrence OTA can be utilized as fundamental building obstruct in a few RF and also microwave applications. This paper presents a study of various trans-conductance amplifiers proposed in the previous years.