Patent ID: 8508293

Claim:
An ASK demodulator, comprising: a rectification circuit configured to receive and rectify an ASK signal to generate a rectified current; an active load circuit coupled to the rectification circuit and configured to receive the rectified current and present an impedance which is inversely proportional to at least a part of the rectified current when a frequency of a base band signal meets a preset condition; and a comparator coupled to the rectification circuit and the active load circuit and configured to receive a reference voltage and a voltage generated based on, at least in part, the rectified current and the impedance, and compare the reference voltage and the generated voltage to generate a demodulated signal; wherein the active load circuit comprises: a first MOSFET with a source coupled to a power supply and a drain coupled to the rectification circuit; a capacitor with a first end coupled to the power supply and a second end coupled to a gate of the first MOSFET; a second MOSFET with a source coupled to the gate of the first MOSFET and the second end of the capacitor, a gate coupled to the drain of the first MOSFET and a drain which is grounded.