It may be easy to find a precision voltage reference for your application; however, a programmable precision reference is another matter. The circuit in Figure 1 yields a precision reference with an LSB of 62.5 µV. The circuit is a 16-bit DAC using three 8-bit digital potentiometers and three CMOS op amps. Each digital potentiometer operates as an 8-bit multiplying DAC. On the left side of Figure 1, two digital potentiometers, IC3A and IC3B, span across VREF to ground, and the wiper outputs are connected to the noninverting inputs of two amplifiers, IC4A and IC4B.