Voltage averaging technique for improving the resolution of two-capacitor DAC

A simple and efficient method to eliminate the effect of capacitor mismatch for a two-capacitor digital-to-analog converter (DAC) is presented. The method expands the conventional two-capacitor DAC by adding only one sample-and-hold amplifier and several switches. The role of the two capacitors is interchanged for every bit being converted. By averaging the voltage across the two capacitors, the maximum error caused by capacitor mismatch is reduced greatly. Simulation indicates that the resolution for 20 bit conversion can be achieved at 0.1% relative capacitor mismatch with the proposed method.