Low-voltage high-gain differential OTA for SC circuits

A new differential operational transconductance amplifier (OTA) for SC circuits that operates with a supply voltage of less than two transistor threshold voltages is presented. Its simplicity relies on the use of a low-voltage regulated cascode circuit, which achieves very high output impedance under low-voltage restrictions. The OTA has been designed to operate with a supply voltage of V_DD=1.5 V, using a 0.6 μm CMOS technology with transistor threshold voltages of V_TN=0.75 V and V_TP=-0.85 V. Post-layout simulation results for a load capacitance (C_L) of 2 pF show a 75 MHz gain-bandwidth product and 100 dB DC gain with a quiescent power consumption of 750 μW.