Doherty amplifier

An integrated Doherty amplifier for amplifying an input signal at an operating frequency, comprising:

• a main amplifier;
• at least a first and a second peak amplifier, each of the amplifiers comprising a gate for receiving the input signal, a source and a drain for providing an amplified signal;
• a first input phase shifter between the gate of the main amplifier and the gate of the first peak amplifier;
• a second input phase shifter between the gate of the first peak amplifier and the gate of the second peak amplifier, wherein the first input phase shifter and second input phase shifter are each configured to shift the phase of the input signal by 90 degrees at the operating frequency;
• a first capacitor configured to be coupled between the drain of the first peak amplifier and ground;
• a first output phase shifter between the drain of the main amplifier and the drain of the first peak amplifier, wherein the first output phase shifter in combination with the first capacitor is configured to shift the phase of the amplified signals from the main amplifier by 90 degrees at the operating frequency;
• and
• a second output phase shifter between the drain of the first peak amplifier and the drain of the second peak amplifier, wherein the second output phase shifter in combination with the first capacitor is configured to shift the phase of the amplified signals from the first peak amplifier by 90 degrees at the operating frequency.