High-Resistance Resistor Consisting of a Subthreshold CMOS Differential Pair

Abstract

We propose a CMOS circuit that can be used as an equivalent to resistors. This circuit uses a simple differential pair with diode-connected MOSFETs and operates as a high-resistance resistor when driven in the subthreshold region of MOSFETs. Its resistance can be controlled in a range of 1-1000MΩ by adjusting a tail current for the differential pair. The results of device fabrication with a 0.35-µm 2P-4M CMOS process technology is described. The resistance was 13MΩ for a tail current of 10nA and 135MΩ for 1nA. The chip area was 105µm × 110µm. Our resistor circuit is useful to construct many high-resistance resistors in a small chip area.