Constant-gm Bias Circuit without Off-Chip Components

This paper presents a process, voltage, and temperature (PVT)-independent constant-gm bias circuit, designed in 0.18 mu m 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 degrees C to 85 degrees C is +/- 570ppm/degrees C. The variation of gm is 1.1%/V across supply voltage range of 1.5V to 2.5V at 27 degrees C. The whole circuit consumes 83 mu W with supply voltage of 1.8V.