Power amplifier and radio transmitter
AssigneeHitachi Kokusai Electric Inc.
InventorToshiyuki NAGASAKU
Life of this patent
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Abstract
A power amplifier includes a carrier amplifier that operates from when an input signal is small, a peak amplifier that starts to operate when the input signal becomes large, a phase adjusting circuit that adjusts phases of an output of the carrier amplifier and an output of the peak amplifier, an impedance transforming line that transforms a load of the carrier amplifier when the input signal is small, and has a characteristic impedance close to an optimum load impedance of the carrier amplifier, and a circuit that is arranged between the output of the carrier amplifier and the impedance transforming line and reduces an output capacitance of the carrier amplifier.
Claims9
A power amplifier includes:
- a carrier amplifier that amplifies an input signal;
- a peak amplifier that starts to amplify the input signal when a signal level of the input signal becomes a predetermined level or more;
- a phase adjusting circuit that adjusts phases of an output of the carrier amplifier and an output of the peak amplifier;
- an impedance transforming line that transforms a load of the carrier amplifier when the signal level of the input signal is smaller than the predetermined level;
- a first inductance having one terminal coupled to an output of a first transistor forming the carrier amplifier and another terminal grounded in an alternating-current manner;
- and
- a serial resonant circuit in which a second inductance and a first capacitance are coupled in series between the first inductance and the impedance transforming line, wherein
- the impedance transforming line has an approximately equal characteristic impedance to an optimum load impedance of the carrier amplifier when the signal level is the predetermined level or more, at a coupling point of the impedance transforming line and the serial resonant circuit.
Dependencies are inferred from the claim text.