Patent ID: 8928405
Filing Date: 2015-01-06
Classification: H03F,H03G

Abstract:
1. A circuit for amplifying the power of a signal, the circuit comprising a power amplifier, a transformer and a load; wherein the transformer comprises a primary inductor and a secondary inductor, the primary inductor being coupled to, and capable of being driven by, the power amplifier, and the secondary inductor coupled to, and capable of driving, the load; wherein a first one of the primary and secondary inductors is a variable inductor whose inductance is variable responsive to a control input in order to change the output power of the amplifier; wherein the variable inductor comprises a plurality of excludable inductors and a switching arrangement operable to selectively exclude one or more of the excludable inductors from contributing to the variable inductor in order to alter the inductance of the variable inductor; wherein the variable inductor comprises first and second ends and the switching arrangement comprises first and second switching mechanisms connected, respectively, to the first and second ends and the plurality of excludable inductors are connected in parallel between the first and second switching mechanisms; and wherein a second one of the primary and secondary inductors is nested with the excludable inductors.