In order to achieve a circuit device capable of stably supplying an antenna with electric power in a broad power range to output a transmission signal, the circuit device includes a current source adapted to supply a first current in a first operation mode, and supply a second current higher than the first current in a second operation mode, and a drive section supplied with the electric power from the current source, and adapted to perform drive for outputting a transmission signal to an antenna via a matching circuit.

A Domino circuit for impedance tuning circuit can include a first node and a second node, and an inductance circuit including an inductor and a first switch connected in series such that the inductor is connected to the first node and the first switch is connected to the second node. The inductance circuit can further include a second switch implemented between ground and a third node between the inductor and the first switch, such that the inductance circuit is capable of providing a series inductance path between the first and second nodes or a shunt inductance path between the third node and the ground.

A self-tuning device and related method includes a first voltage indicative of a first magnitude of an input signal to an antenna stored in a first capacitor when a variable capacitor bank coupled to the antenna is in a first configuration and a second voltage indicative of a second magnitude of the input signal when the variable capacitor bank is in a second configuration are compared. A first output signal based on the comparison is used to determine, the first configuration of the variable capacitor bank results in an optimized configuration of the variable capacitor bank. The variable capacitor bank is configured in the first configuration.