A self-tuning RFID device having an input capacitance that is adjustable in response to a detected signal. The self-tuning RFID device preferably comprises a variable capacitance RFID chip coupled to an inductor, and an input circuit driven by the detected signal from the variable capacitance RFID chip. A change in capacitance with the detected signal is delayed by a specific amount of time, thereby allowing the self-tuning RFID device to function as a dual mode EAS and RFID tag. The ESA functionality can be deactivated by a high field at or near its resonance frequency without disabling the RFID functionality. The effect of the high field may change the input capacitance permanently changing its resonance.