RFID tag circuits, tags, and methods are provided for backscattering a received RF wave using a controllable admittance difference between the ON state and the OFF state. The admittance difference is controlled responsive to a control signal. In some embodiments, the control signal is generated responsive to a command. In others, the control signal is generated responsive to detecting the power level of the received RF wave. In those, the inherent behavior of the admittance difference can be shaped as desired. For example, it can be such that the backscatters with advantageously more power when it is away from the reader, and with less power when it is close to the reader, so as to meet regulatory requirements.