RADIO FREQUENCY SIGNAL POWER AMPLIFICATION CIRCUIT

An RF amplifier includes a branch with an inductor series-connected with a capacitor between first and second power supply nodes, a junction point between the inductor and capacitor forming an output node. A further branch includes a MOS transistor series-connected with a switch between the output node and the second power supply node. The switch has a control node coupled to receive a first input signal. The MOS transistor has a gate coupled to receive a second input signal. A control circuit applies the power supply voltage as the second input signal when a frequency/phase-modulated signal is applied as the first input signal. The control circuit further applies a variable signal as the second input signal when a radio frequency signal of constant frequency, phase, and amplitude is applied as the first input signal, and in this mode the MOS transistor is constrained to operate as a current source.