Low noise amplifier

A low noise amplifier comprising:

• a first circuit block suitable for converting a first amplifier input voltage signal into current,
• a second circuit block adapted to divide the current coming from said first block, said second block being controlled by a second voltage signal, said first and second blocks conferring a variable voltage gain to the amplifier,
• at least one first and at least one second resistors and a feedback network, said at least one first resistor connected with a first output terminal of said second block and with a supply voltage, and said at least one second resistor being connected between said at least one first and at least one second output terminals of said second block, and said feedback network being coupled with said at least one first terminal and with said first circuit block, and said at least one second terminal being coupled with at least one output terminal of said low noise amplifier,
• wherein said first block comprises a first and a second transistors forming a first differential stage, the input terminals of said transistors being the input terminals of the amplifier,
• said second block comprises a third and a fourth transistors forming a second differential stage and a fifth and a sixth transistors forming third differential stage, said third and said sixth transistors having a first input terminal in common and said fourth and said fifth transistors having a second input terminal in common and said second voltage signal being applied between said first and said second input terminals,
• said amplifier comprising two first resistors and two second resistors and consequently said second block having two first output terminals and two second output terminals, one of said first output terminals being the output terminal of said fourth transistor and the other of said two first output terminals being the output terminal of said fifth transistor, one of said two second output terminals being the output terminal of said third transistor and the other of said two second output terminals being the output terminal of said sixth transistor, and
• said feedback network comprising two resistors each coupled with one of said two first input terminals of the second block and with one of said two respective input terminals of the first and second transistor of the first block, and said two output terminals of the second block being coupled with two respective output terminals of the amplifier.

An integrated circuit including at least one low noise amplifier, said low noise amplifier comprising:

• a first circuit block suitable for converting a first amplifier input voltage signal into current, at least one input terminal of said first circuit block receiving said first amplifier input voltage;
• a second circuit block adapted to divide the current coming from said first circuit block, said second circuit block being controlled by a second voltage signal, and said first and second circuit blocks conferring a variable voltage gain to the amplifier;
• at least one first resistor;
• at least one second resistor;
• and
• a feedback network,
• wherein said at least one first resistor is connected with at least one first output terminal of said second circuit block and with a supply voltage,
• said at least one second resistor is connected between said at least one first output terminal and at least one second output terminal of said second circuit block,
• said feedback network is coupled with said at least one first output terminal and is directly connected to said at least one input terminal of said first circuit block which receives the first amplifier input voltage, so as to obtain a constant input impedance, and
• said at least one second output terminal is coupled with at least one output terminal of said low noise amplifier.