Variable gain amplifier

A variable gain amplifier comprising:

• a differential amplifier circuit having a pair of input terminals and a pair of output terminals, the differential amplifier circuit includes a first differential amplifier circuit and a second differential amplifier circuit;
• a first variable attenuation circuit connected between at least one of the pair of input terminals and the pair of output terminals of the first differential amplifier circuit and capable of switching a resistance value on the basis of a control signal which is input from outside;
• a second variable attenuation circuit connected between the pair of output terminals of the second differential amplifier circuit at a preceding stage of the first differential amplifier circuit including the pair of input terminals to which the first variable attenuation circuit is connected, and capable of switching a resistance value between the pair of output terminals on the basis of a control signal which is input from the outside;
• and
• an inter-stage matching circuit provided between the first variable attenuation circuit and the second variable attenuation circuit;
• wherein
• the differential amplifier circuit includes N (N is an integer equal to or greater than 2) differential amplifier circuits cascade-connected to each other in a propagation direction of a high-frequency signal,
• the first variable attenuation circuit is connected between the pair of input terminals of at least one of the first differential amplifier circuits in second to Nth stages counted from the pair of input terminals of the variable gain amplifier,
• equivalent resistances of the first variable attenuation circuit and the second variable attenuation circuit have a plurality of levels, and
• a ratio of the equivalent resistance of second variable attenuation circuit to the equivalent resistance of the first variable attenuation circuit at each of the plurality of levels is equal to a ratio of a primary-side inductance of the inter-stage matching circuit to a secondary-side inductance of the inter-stage matching circuit.