Apparatus and methods for radio frequency amplifiers

A front end system for controlling beamforming in an active scanned electronically steered array, the front end system comprising:

• a phase shifter configured to control a phase of a radio frequency (RF) input signal;
• and
• an RF amplifier in series with the phase shifter and configured to amplify the RF input signal to generate an RF output signal at an output node, wherein the RF amplifier comprises:
• a main amplifier stage including a differential output;
• a first differential balun combiner configured to provide a first single-ended RF signal to the output node and to receive a first differential RF signal from the differential output of the main amplifier stage, wherein the first differential balun combiner absorbs an output matching network of the main amplifier stage;
• an auxiliary amplifier stage including a differential output, a first cascode transistor, and a second cascode transistor;
• a transformer component;
• and
• a second differential balun combiner configured to generate a second single-ended RF signal and to receive a second differential RF signal from the differential output of the auxiliary amplifier stage, and to provide the second single-ended RF signal to the output node through the transformer component, the second differential balun combiner including a first conductor directly connected between a drain of the first cascode transistor and a drain of the second cascode transistor, wherein the second differential balun combiner absorbs an output matching network of the first cascode transistor and the second cascode transistor of the auxiliary amplifier stage.

A method of radio frequency (RF) signal amplification, the method comprising:

• amplifying a first differential RF input signal to generate a first differential RF signal using a main amplifier stage;
• providing a first single-ended RF signal from a first differential balun combiner to an output node and receiving the first differential RF signal at the first differential balun combiner, wherein the first differential balun combiner absorbs an output matching network of the main amplifier stage;
• amplifying a second differential RF input signal to generate a second differential RF signal using an auxiliary amplifier stage that includes a first cascode transistor and a second cascode transistor;
• outputting a second single-ended RF signal from a second differential balun combiner and receiving the second differential RF signal at the second differential balun combiner, the second differential balun combiner including a first conductor directly connected between a drain of the first cascode transistor and a drain of the second cascode transistor, wherein the second differential balun combiner absorbs an output matching network of the first cascode transistor and the second cascode transistor of the auxiliary amplifier stage;
• and
• providing the second single-ended RF signal to the output node through a transformer component.