A resettable latched voltage comparator includes a resonant tunneling diode 10 connected in series with an amplifier 14 and a power source 16, and a reset circuit 12 connected between a circuit output terminal 18 and a second power source 20. Amplifier 14 converts the value of the voltage at an input terminal 22 into a proportional current at terminal 24; diode 10 detects the condition when the current at terminal 24 rises above a specific value equal to the resonant peak current of resonant tunneling diode 10; and reset circuit 12 controllably forces the voltage at terminal 18 of the circuit to a value approximately equal to the output voltage of power source 16 at terminal 29, thereby reducing the bias across diode 10 to approximately zero. A flash analog-to-digital converter configuration includes a plurality of comparators 200.sub.i having their reference voltage inputs biased from a series-connected chain of resistors 210.sub.i. The input terminals 22.sub.i of the comparators are coupled for connection to an analog signal source, and the comparator reset terminals 25.sub.i are coupled for connection to a reset control source.