Design of Low-Voltage Two-Stage Single-Ended MOSFET-Only Operational Amplifire

In this paper, the gate-to-bulk capacitance property of MOS transistors (MOSCAPs) is employed to design a high-speed two-stage single-ended MOSFET-only operational amplifier (opamp). Traditional design of two-stage opamps recommends MIM or PIP capacitors to avoid instability in closed-loop applications whilst in the proposed structure, constant capacitor of the opamp is replaced with anti-parallel depletion-mode metal–oxide–semiconductor (MOS) devices. In addition to area efficiency achieved by replacing the capacitor with MOS transistors, the integration of the opamp would become compatible with standard digital CMOS technologies. Cadence simulation results of the circuit in 0.18 μm standard digital complementary metal–oxide–semiconductor (CMOS) technology with a single power supply of 1.2V validate the effectiveness of the proposed structure.

Keywords:

analogue integrated circuit , single-ended , operational amplifier , two-stage , cascode compensation , MOSFET-only , low-voltage , MOSCAPs