A new structure of low-power demodulator named 'separated-Vb' amplitude shift keying (ASK) demodulator is proposed. The circuit is based on the switching behavior of the core digital shaper with different bias voltages, which improves its operation at low modulation indexes and reduces power consumption. This design does not require a comparator or Schmitt trigger, and only a few elements are needed which minimizes the chip area. The design is fabricated in the 0.18μm CMOS process. The core chip area is 0.00144 mm2, and the power consumption is 45μW at a 1.8V power supply. The data rate can be nearly 2.7 Megabits per second (Mbps) at 13.56 MHz.