Low-noise gain switching circuit using tapped inductor

A radio frequency (RF) receiver comprising:

• a receiver front-end circuit capable of receiving an incoming RF signal from an antenna and generating an amplified RF output signal, said receiver front-end circuit comprising:
• a variable gain low-noise amplifier comprising:
• an input transistor having a first ground terminal coupled to ground and an input terminal coupled to said incoming RF signal;
• a first output transistor having a first output terminal coupled to a second output terminal of said input transistor;
• a first switch capable of turning said first output transistor ON and OFF by selectively coupling an input terminal of said first output transistor to one of:
• 1) a first enabling voltage and 2) a first disabling voltage;
• a second output transistor having a first output terminal coupled to said second output terminal of said input transistor;
• a second switch capable of turning said second output transistor ON and OFF by selectively coupling an input terminal of said second output transistor to one of:
• 1) a second enabling voltage and 2) a second disabling voltage;
• and
• an inductor comprising a first inductor terminal coupled to a supply voltage, a second inductor terminal coupled to a second output terminal of said first output transistor, and a first tap point intermediate said first and second inductor terminals coupled to a second output terminal of said second output transistor;
• and
• demodulation circuitry coupled to said receiver front-end circuitry capable of demodulating said amplified RF output signal.

A variable gain low-noise amplifier comprising:

• an input transistor having a first ground terminal coupled to ground and an input terminal coupled to an input signal;
• N output transistors, each of said N output transistors having a first output terminal coupled to a second output terminal of said input transistor;
• N switches, each of said N switches capable of turning a corresponding one of said N output transistors ON and OFF by selectively coupling an input terminal of said corresponding one of said N output transistors to one of:
• 1) an enabling voltage and 2) a disabling voltage;
• and
• an inductor comprising a first inductor terminal coupled to a supply voltage, a second inductor terminal coupled to a second output terminal of a first one of said N output transistors, and N−1 tap points intermediate said first and second inductor terminals, each of said N−1 tap points coupled to a second output terminal of a corresponding one of the remaining N−1 output transistors.