Radio frequency low noise amplifier with automatic gain control

A low noise amplifier comprising:

• a first inductor having a first terminal coupled to a first power supply voltage terminal, and a second terminal forming a first output voltage signal thereon;
• a first transistor having a first current electrode coupled to said second terminal of said first inductor, a control electrode coupled to said first power supply voltage terminal, and a second current electrode;
• a second transistor having a first current electrode coupled to said second current electrode of said first transistor, a control electrode for receiving a first input signal, and a second current electrode;
• a second inductor having a first terminal coupled to said second current electrode of said second transistor, and a second terminal coupled to a second power supply voltage terminal;
• a third inductor having a first terminal coupled to said first power supply voltage terminal, and a second terminal forming a second output voltage signal thereon;
• a third transistor having a first current electrode coupled to said second terminal of said third inductor, a control electrode coupled to said first power supply voltage terminal, and a second current electrode;
• a fourth transistor having a first current electrode coupled to said second current electrode of said third transistor, a control electrode for receiving a second input signal, and a second current electrode;
• a fourth inductor having a first terminal coupled to said second current electrode of said fourth transistor, and a second terminal coupled to said second power supply voltage terminal;
• and
• an attenuation device coupled between said first current electrode of said first transistor and said first current electrode of said third transistor, and having a control input terminal for receiving a control voltage thereon.

A method for operating a low noise amplifier with automatic gain control comprising the steps of:

• determining a power level of an output signal of the low noise amplifier;
• providing a control voltage in response to said power level;
• biasing the low noise amplifier to operate in a constant transconductance mode in response to said control voltage being less than a predetermined voltage;
• and
• biasing the low noise amplifier to operate in a constant saturation voltage mode in response to said control voltage being greater than said predetermined voltage.

A low noise amplifier comprising:

• a first transconductance device having a control electrode for receiving a first input signal, and a first current electrode;
• a first load device having a first terminal coupled to a first power supply voltage terminal and a second terminal coupled to said first current electrode of said first transconductance device and forming a first output voltage signal thereon;
• a second transconductance device having a control electrode for receiving a second input signal, and a first current electrode;
• a second load device having a first terminal coupled to said first power supply voltage terminal and a second terminal coupled to said first current electrode of said second transconductance device and forming a second output voltage signal thereon;
• an attenuation device coupled between said first current electrode of said first transconductance device and said first current electrode of said second transconductance device, and having a control input terminal for receiving a control voltage thereon;
• and
• a biasing network coupled between said control electrodes of said first and second transconductance devices, said biasing network comprising:
• a first resistor having a first terminal coupled to said control electrode of said first transconductance device, and a second terminal;
• a second resistor having a first terminal coupled to said control electrode of said second transconductance device, and a second terminal coupled to said second terminal of said first resistor;
• a current source having a first terminal coupled to said first power supply voltage terminal, and a second terminal;
• and
• a transistor having a first current electrode coupled to said second terminal of said current source, a control electrode coupled to said first current electrode thereof, and a second current electrode coupled to a second power supply voltage terminal.