Variable gain amplifier
AssigneeSumitomo Electric Industries, Ltd.
InventorNaoki Itabashi
Life of this patent
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Abstract
A variable gain amplifier capable of stabilizing an average output potential of a differential output signal, improving power efficiency over a wide range of an amplitude of the differential input signal, and suppressing deterioration of a distortion rate is provided. The variable gain amplifier includes an amplifying circuit configured to amplify a differential input signal with a gain according to a gain control signal, and a current control circuit. The amplifying circuit has a first current source supplying a source current. The current control circuit adjusts a magnitude of the source current of the first current source according to a magnitude of the gain control signal.
Claims10
A variable gain amplifier amplifying a differential input signal including a positive phase component and a negative phase component having phases opposite to each other with a gain according to a gain control signal, and outputting a differential output signal including a positive phase component and a negative phase component having phases opposite to each other, the variable gain amplifier comprising:
- an amplifying circuit including
- a first current source having a first end and a second end and supplying a source current flowing from the first end to the second end;
- a first differential circuit being electrically connected to the first end of the first current source and splitting the source current into a first current and a second current according to the differential input signal;
- a second differential circuit being electrically connected to the first differential circuit and splitting the first current into a third current and a fourth current according to a magnitude of the gain control signal;
- a third differential circuit being electrically connected to the first differential circuit, and splitting the second current into a fifth current and a sixth current according to the magnitude of the gain control signal so that a ratio of the fifth current to the sixth current is equal to a ratio of the fourth current to the third current;
- a first resistor being electrically connected to the second differential circuit and generating the negative phase component of the differential output signal according to a magnitude of a voltage drop occurring due to a flow of the fourth current;
- and
- a second resistor being electrically connected to the third differential circuit and generating the positive phase component of the differential output signal according to a magnitude of a voltage drop occurring due to a flow of the fifth current;
- and
- a current control circuit configure to control the first current source, decrease the source current when the gain control signal increases the gain, and increase the source current when the gain control signal decreases the gain.
Dependencies are inferred from the claim text.