In this paper, an amplitude shift keying (ASK) demodulator with 100% modulation depth is proposed. In order to achieve the higher power and wider reading range the designed ASK demodulator works in the ultra-high frequency. In this design, the average detector and voltage divider are used in order to define the appropriate threshold voltage level for the radio frequency input signal which leads to the accurate data detecting even at long distances between the tag and reader. In addition, for diminishing the power dissipation of the proposed demodulator, an enable input is used in the buffer and comparator. This circuit is simulated in 0.18 μm complementary metal–oxide–semiconductor (CMOS) technology with Cadence software. Its power dissipation and chip area are 3.9 nW and 0.0025 mm2, respectively.