Power amplifier

A power amplifier comprising:

• a splitter configured to split a first signal into a second signal and a third signal, the third signal being delayed from the second signal by equal to or greater than 90° and less than 180°;
• a first amplifier configured to amplify the second signal and to output a fourth signal when a power level of the first signal is equal to or greater than a first level;
• a second amplifier configured to amplify the third signal and to output a fifth signal when the power level of the first signal is equal to or greater than a second level, the second level being greater than the first level;
• and
• a hybrid coupler comprising a first transmission line and a second transmission line,
• wherein the first transmission line is configured to receive the fourth signal at a first terminal of the first transmission line,
• wherein the second transmission line is configured to receive the fifth signal at a first terminal of the second transmission line,
• wherein the second transmission line is open at a second terminal of the second transmission line, and
• wherein the first transmission line is configured to output, from a second terminal of the first transmission line, an amplified first signal, the amplified first signal being a combination of the fourth signal and the fifth signal.