A system for identifying and selecting the maximum or minimum value of a single signal or a subset of signals from among a larger set of signals. The system includes an amplifier for each subset of signals. The outputs of the amplifiers are connected in common. Feedback loops from the common output to an input cause all amplifiers, except the one with the largest input signal, to operate in the nonlinear region. Each amplifier is monitored to determine whether or not it is operating linearly.