Low-noise amplifier with gain enhancement

A low-noise amplifier (“LNA”), comprising:

• a plurality of cascode gain stages for increasing an amplitude of a radio frequency (“RF”) input signal, each of the cascode gain stages including
• a first transistor having a source coupled to ground and a gate coupled an input node of the respective gain stage for receiving an RF input signal to the respective gain stage, and
• a second transistor having a source coupled to a drain of the first transistor and a drain coupled to an output node of the respective gain stage;
• at least one inductive gate network having a non-zero input impedance and including at least one passive circuit element coupled to a gate of the second transistor in at least one of the plurality of cascode gain stages;
• and
• at least one variable gain network coupled to a gate of the second transistor in at least one of the plurality of cascode gain stages, the at least one variable gain network including
• an inductor for boosting a gain of the cascode gain stage to which the at least one variable gain network is coupled,
• a capacitor coupled to the inductor for blocking a direct current (“DC”) voltage, and
• a third transistor coupled to the inductor and to the capacitor, the third transistor configured to selectively couple the inductor to the gate of the second transistor of the cascode gain stage to which the at least one variable gain network is coupled in response to a control signal received at a gate of the third transistor to increase an inductance at the gate of the second transistor of the cascode gain stage to which the at least one variable gain network is coupled.

A method, comprising:

• receiving a first radio frequency (“RF”) signal at an input node for a first cascode gain stage, a first inductive gate network having a non-zero input impedance and at least one passive circuit device is coupled to a gate of a first common gate transistor of the first cascode gain stage;
• increasing an amplitude of the first RF signal at the first cascode gain stage to produce a second RF signal;
• outputting the second RF signal having an amplitude greater than an amplitude of the first RF signal to an output node of the first cascode gain stage coupled to the first common gate transistor
• receiving the second RF signal at an input node for a second cascode gain stage;
• selectively coupling a variable gain network to a gate of a second common gate transistor of the second cascode gain stage in response to receiving a control signal at a gate of a third transistor to increase an impedance at the gate of the second transistor thereby further increasing the amplitude of the second RF signal to produce a third RF signal.

A method, comprising

• receiving a first radio frequency (“RF”) signal at an input node for a first cascode gain stage,
• selectively coupling a variable gain network to a gate of a first common gate transistor of the first cascode gain stage in response to receiving a control signal at a gate of a transistor to increase an impedance at the gate of the first common gate transistor thereby increasing the amplitude of the first RF signal to produce a second RF signal;
• increasing an amplitude of the second RF signal at a second cascode gain stage to produce a third RF signal, the second cascode gain stage including a second common gate transistor to which a first inductive gate network is coupled, the first inductive gate network having a non-zero input impedance and at least one passive circuit device coupled to the gate of the second common gate transistor of the second cascode gain stage;
• and
• outputting the third RF signal having an amplitude greater than an amplitude of the second RF signal to an output node of the second cascode gain stage coupled to the second common gate transistor.