Apparatus and method for amplifying a signal

A method of amplifying an input signal, the method of amplifying comprising the steps of:

• receiving said input signal at a signal input of a variable attenuator;
• attenuating said input signal forming an attenuated signal;
• amplifying said attenuated signal forming a amplified signal;
• amplifying said amplified signal in a first Doherty amplifier forming a first Doherty output signal;
• detecting a total signal in a detector forming a detected output signal, said total signal comprising at least said first Doherty output signal;
• comparing said detected output signal to a predetermined controller threshold in a controller;
• generating a first control signal and a second control signal in said controller if detected output signal falls below said predetermined controller threshold;
• generating a switching regulator output voltage in a switching regulator based upon said first control signal;
• modifying a voltage of said first Doherty amplifier based upon said switching regulator output voltage;
• and
• modifying a voltage of said variable attenuator based upon said second control signal.

An amplifier circuit comprising:

• a first Doherty amplifier having an input, a first Doherty control input, and an output;
• a second Doherty amplifier having an input coupled to said output of said first Doherty amplifier, an output, and a second Doherty control input;
• a detector having a detector input coupled to detect a second Doherty output signal of said output of said second Doherty amplifier, and an output;
• a controller having an input coupled to said output of said detector, and an output;
• and
• a switching regulator having an input coupled to said output of said controller, and first and second switching regulator output, the first switching regulator output coupled to said first Doherty control input and the second switching regulator output coupled to said second Doherty control input.

A method of amplifying an input signal, the method of amplifying comprising the steps of:

• receiving said input signal at an input of a first Doherty amplifier;
• receiving a first supply voltage at a first Doherty control input of said first Doherty amplifier;
• amplifying said input signal in said first Doherty amplifier forming a first Doherty output signal;
• receiving said first Doherty output signal at an input of a second Doherty amplifier;
• receiving a second supply voltage at a second Doherty control input of said second Doherty amplifier;
• amplifying said first Doherty output signal in said second Doherty amplifier forming a second Doherty output signal;
• detecting a total signal, forming a detected output signal, said total signal comprising at least said second Doherty output signal;
• comparing said detected output signal to a predetermined controller threshold in a controller;
• generating a control signal in said controller if said detected output signal falls below said predetermined controller threshold;
• generating a first supply voltage in a switching regulator based upon said control signal;
• modifying a voltage of said first Doherty amplifier based upon said first supply voltage;
• generating a second supply voltage in said switching regulator based upon said control signal;
• and
• modifying a voltage of said second Doherty amplifier based upon said second supply voltage.