A circuit includes a peak detector, a diode, a dynamic clamp circuit, and an offset correction circuit. The peak detector generates a voltage on the peak detector output proportional to a lowest voltage on the peak defector input. The anode of the diode is coupled to the peak detector input. The dynamic clamp circuit is coupled to the peak detector input and is configured to clamp a voltage on the peak detector input responsive to a voltage on the diode's anode being greater than the lowest voltage on the peak detector's input. The offset correction circuit is coupled to the peak detector output and is configured to generate an output signal whose amplitude is offset from an amplitude of the peak detector output.