Sub-threshold R-MOSFET tunable resistor technique

An R-MOSFET resistor structure that enables extension of the MOSFETs' operation into sub-threshold region while preserving good linearity performance is presented. The technique essentially relies upon a linear current division between two nonlinear branches each comprising a linear resistor and a MOSFET operating at sub-threshold inversion. The feasibility of the sub-threshold R-MOSFET structure is demonstrated via breadboard experiment using array transistors, and via simulation using a 0.18 µm CMOS process.