A circuit for demodulating an input signal is described. The circuit may be configured to demodulate signals modulated with amplitude-based modulation schemes, such as amplitude shift keying (ASK), such that information is encoded in the amplitude of the signals. The circuit may comprise an amplitude detector for extracting the envelope of a received amplitude-modulated signal, a phase/frequency detector for detecting phase and/or frequency shifts, and a selector configured to select one between the output of the amplitude detector and the output of the phase/frequency detector. The selector may be controlled by a control circuit including a delay unit.