In this paper, an Amplitude Shift Keying (ASK) demodulator circuit for Near Field Communication (NFC) target mode or Radio Frequency Identification (RFID) tag is designed by using sample and hold method. It features envelope detector, switch capacitor filter, dynamic comparator, clock extractor and phase generator. This demodulator was demonstrated and simulated in TSMC 0.18um CMOS technology with an average power of 32uW power consumption at 13.56Mbps Non-Return-to-Zero (NRZ) date rate for a carrier frequency of 13.56MHz. The minimum input voltage swing is 200mVpp.