A Bulk-Driven Variable Gain OTA in 180nm CMOS Technology

In this paper, an operational transconductance amplifier (OTA) is designed, simulated and configured so that input dynamic range is improved by bulk-driven technique of the input transistors. The bulk-driven structure is used in the proposed OTA to stabilize the transconductance and to achieve a high linearity. By changing the control voltage and the input common-mode voltage, the voltages and currents of the circuit are changed so that the transconductance and the voltage gain are changed linearly. Also, setting a reference voltage in the circuit can greatly reduce the destructive effects of undesired changes in the circuit operation during fabrication process. The proposed OTA is designed in 180 nm CMOS technology and required only 0.5 V supply voltage. The simulation results show the OTA voltage gain is varied from 0 dB to 14.2 dB by changing the control voltage from 0 to 0.5 V. Moreover, the input common-mode voltage of the OTA can be changed in the range of 0.125 to 0.375V and without linear degradation. The proposed OTA is dissipated 250 nW and makes it suitable for low-power applications.