An analog-to-digital converter includes a comparator configured to receive a first input signal and a second input signal, in which at least one of the input signals is received between two transistors, each of the transistors being in common-gate configuration. A method for comparing input signals performed by a comparator circuit includes: receiving a first input signal between a drain terminal of a first transistor of the comparator circuit and a source terminal of a second transistor of the comparator circuit; receiving a second input signal; and outputting a value based on a comparison of the first input signal and the second input signal.