A circuit for signal decoding in RFID or wireless power charging is provided in the present invention. The implement of the present invention is to add a current sense resistor connected to an upper switch or a lower switch the up arm switch or low arm switch to decode the signal on the current sense resistor. Since the error would occur in the original voltage decoder of the wireless power or RFID when the load is heavy and voltage signal swing is large, such that the charge status and then the off-line status cyclically occur and then the charge status . . . occurs in cycle when the mobile device is charging under charge. Since the present invention uses the voltage and current for decoding at the same time, the decoding would be succeed whenever the load is light or heavy.