Radio-frequency amplifier circuitry with improved transmit and receive performance

A method of operating an amplifier, comprising:

• with a first input transistor of the amplifier, receiving a radio-frequency signal;
• with a first cascode transistor coupled in series with the first input transistor, outputting an amplified radio-frequency signal onto a first output terminal of the amplifier;
• with a balun coupled to the first output terminal, receiving a positive power supply voltage for powering the amplifier in a transmit mode during which the amplifier is activated;
• and
• with the balun, receiving the positive power supply voltage for reverse biasing a source-drain terminal of the first cascode transistor in a receive mode during which the amplifier is deactivated.

An amplifier comprising:

• a first input transistor coupled between a first output terminal of the amplifier and a ground power supply line, the first input transistor having a first threshold voltage;
• a balun coupled to the first output terminal and a positive power supply line;
• a first capacitor coupled to the first output terminal;
• and
• a first switching transistor coupled in series with the first capacitor and having a second threshold voltage lower than the first threshold voltage.