A physiological signal processing circuit includes an amplifier, an analog-to-digital converter, and a physiological characteristic detector circuit. The amplifier is configured to amplify an analog physiological signal of a user for providing an amplified signal. The analog-to-digital converter is coupled to the amplifier, and is configured to convert the amplified signal to a digital signal. The physiological characteristic detector circuit is coupled to the analog-to-digital converter, and configured to detect a physiological characteristic of the user from the digital signal so as to provide an output signal.
