Linear high-frequency amplifier with high input impedance and high power efficiency

A linear high-frequency amplifier, which comprises:

• a single-ended output stage having a control terminal and an output terminal;
• a push-pull emitter follower stage having first and second input terminals, and an output terminal coupled to the control terminal of said output stage;
• a phase-splitter stage having an input terminal, first, second and third transistors having their main current paths coupled in series between a power supply terminal and a ground terminal, and first and second low-impedance split-phase output terminals coupled to the first and second input terminals of said emitter follower stage, said first split-phase output terminal being coupled to a point between said first and second transistors and said second split-phase output terminals being coupled to a point between said second and third transistors;
• a bias-current control stage directly connected to said phase-splitter stage for providing bias currents to said at least two transistors of said phase-splitter stage;
• and
• a linear voltage-to-current converter stage having an input terminal for receiving a high-frequency input voltage and an output terminal connected to the input terminal of said phase-splitter stage for providing a high-frequency current signal proportional to said input voltage thereto.