4 to 2 ADC

This is the analog front end for a 3-bit flash ADC, perhaps the simplest implementation of an analog to digital converter. Following this analog circuit would be a digital decoder to go from the comparator outputs to a 3-bit binary number. My favorite resource for learning more about flash ADCs is the Maxim Integrated app note: https://www.maximintegrated.com/en/app-notes/index.mvp/id/810