Linearity Enhancement of Operational Transconductance Amplifier Using Source Degeneration

The signal to noise ratio and resolution of an analog to digital converter is governed by the linearity constraints of the basic building block, which is the Operational Transconductance Amplifier (OTA). The OTA design is based on MOS transistors that are inherently non linear and lead to performance deterioration. To overcome the non-linearities imposed by the OTA a resistive source degeneration technique is proposed. The use of linearization techniques leads to a tradeoff between transconductance and gain of the amplifier. The proposed Source Degenerated OTA (SDOTA) achieves Third order Intermodulation (IM3) of -62dB at a high frequency range of 70 MHz with an effective Transconductance of 655.8 μA/V. The SDOTA offers a gain of 14dB at a Unity Gain Frequency of 4.7 GHz and is implemented in 180nm CMOS technology.