Constant-gm bias circuit without off-chip components

This paper presents a process, voltage, and temperature (PVT)-independent constant-gm bias circuit, designed in 0.18μm CMOS technology. In this paper, the conventional precise off-chip resistor is replaced by a MOSFET operating in triode region with a novel bias circuit, which behaves like a PVT-independent resistor. Simulations show that the maximum gm variation across process corners is ±5.2%, and the worst temperature coefficient across temperature range of -40°C to 85°C is ±570ppm/°C. The variation of gm is 1.1%/V across supply voltage range of 1.5V to 2.5V at 27°C. The whole circuit consumes 83μW with supply voltage of 1.8V.