Voltage controlled resistor for mismatch adjustment in analog CMOS circuits

A Voltage Controlled Resistor (VCR) scheme is demonstrated for use in precision analog applications on standard CMOS processes. This technique utilizes a metal or poly overlay across an n-well resistor field region to slightly modulate the well resistivity. This scheme is quite useful in data converters employing dynamic element matching and amplifiers employing offset cancellation as the maximum adjustable change in resistance is only slightly larger than typical component mismatches. This small voltage variability allows for simple but very precise calibration compared to traditional methods. A macro-model of the VCR is proposed based on device simulation results from ATLAS^TM . Simulation of this device in a dynamic element matching circuit is also demonstrated