Amplifiers and amplifier modules having stub circuits

An amplifier module comprising:

• a multi-layer printed circuit board (PCB);
• a first power transistor die mounted at a top surface of the multi-layer PCB, the first power transistor die configured as a carrier amplifier;
• a second power transistor die mounted at the top surface of the multi-layer PCB, the second power transistor die configured as a peaking amplifier;
• an impedance inversion element coupled between an output of the first power transistor die and an output of the second power transistor die, a combining node formed at the output of the second power transistor die;
• a first stub circuit coupled at the combining node, the first stub circuit comprising a first stripline having a first end coupled at the combining node, the first stub circuit configured to have an electrical length of approximately 90 degrees;
• and
• a second stub circuit coupled at the combining node in parallel with the first stub circuit, the second stub circuit comprising a second stripline having a first end coupled at the combining node, the second stub circuit configured to have an electrical length of approximately 60 degrees.

A Doherty amplifier comprising:

• a multi-layer printed circuit board (PCB);
• a carrier amplifier die mounted at a top surface of the multi-layer PCB;
• a peaking amplifier die mounted at the top surface of the multi-layer PCB;
• an impedance inversion element coupled between a drain terminal of the carrier amplifier die and a drain terminal of the peaking amplifier die, a combining node formed at the drain terminal of the peaking amplifier die;
• a first stub circuit coupled at the combining node, the first stub circuit comprising a first stripline formed from a first conductive layer of the PCB, the first stub circuit configured to have an electrical length of approximately 90 degrees;
• and
• a second stub circuit coupled at the combining node in parallel with the first stub circuit, the second stub circuit comprising a second stripline formed from a second conductive layer of the PCB different from the first conductive layer, the second stub circuit configured to have an electrical length of approximately 60 degrees.