Patent ID: 6933779

Claim:
A variable gain low noise amplifier comprising: a first amplifying cell including a first terminal and second terminal being connected to an output terminal, said first amplifying cell being configured to amplify a signal from an input terminal being input to said first terminal and output to said second terminal in a high gain mode; a second amplifying cell including a first terminal and second terminal being connected to said output terminal, said second amplifying cell being configured to amplify said signal being input to said first terminal of said second amplifying cell and output to said second terminal of said second amplifying cell in a low gain mode; a selectively matching circuit including a first terminal being connected to said input terminal and a second terminal being connected to said first terminal of said first amplifying cell, said selectively matching circuit being configured to change selectively an input impedance of said first amplifying cell, said selectively matching circuit being configured to change said input impedance to maximize a power of said signal in said high gain mode, and to minimize said power of said signal in said low gain mode; a first switch being connected to said input terminal and said first terminal of said second amplifying cell, said first switch being configured to transmit said signal applied to said input terminal to said first terminal of said second amplifying cell in said low gain mode; and a second switch connecting said input terminal and said output terminal.