Broadband variable gain amplifier with high linearity and variable gain characteristic

A variable gain amplifier comprising:

• an amplification unit being configured to amplify an input signal applied to an input terminal and to output an amplified signal to an output terminal;
• and
• a gain control unit being connected between said input and output terminals, and being configured to control gain of said amplification unit, said gain control unit including,
• a variable resistance unit having a resistance value being varied according to a control signal, said variable resistance unit including,
• a transistor having first, second, and third terminals, wherein quantity and direction of current flowing from said second terminal to said third terminal varying dependant on the control voltage applied to said first terminal,
• a first capacitor and a first resistor being connected in series between said input terminal and said third terminal of said transistor, and
• a second capacitor and a second resistor being connected in series between said output terminal and said second terminal of said transistor, and
• a broadband matching unit being configured to provide an optimal impedance characteristic to said input terminal of said amplification unit in a broad band, said variable gain resistance unit and said broadband matching unit being connected in parallel.

A variable gain amplifier comprising:

• an amplification unit being configured to amplify an input signal applied to an input terminal and to output an amplified signal to an output terminal;
• and
• a gain control unit being connected between said input and output terminals, and being configured to control gain of said amplification unit, said gain control unit including,
• a variable resistance unit having a resistance value being varied according to a control signal, and
• a broadband matching unit being configured to provide an optimal impedance characteristic to said input terminal of said amplification unit in a broad band, said variable gain resistance unit and said broadband matching unit being connected in parallel, said broadband matching unit including a resistor, an inductor, and a capacitor being connected in series.

A variable gain amplifier operating in a high gain mode and a low gain mode comprising:

• an amplification unit for amplifying an input signal applied to an input terminal and outputting an amplified signal to an output terminal;
• a broadband matching unit connected between the input terminal and the output terminal for proving an optimal impedance characteristic to the input terminal in the high gain mode;
• an attenuation unit connected between the input terminal and the output terminal for attenuating the input signal and outputting an attenuated signal to the output terminal in the low gain mode;
• and
• means connected to the input terminal for activating said amplification unit in the high gain mode.