US 6,714,075 B2 · Variable gain amplifier and filter circuit

Abstract

The variable gain amplifier of the invention includes an input node pair, a first output node pair, a voltage-current converter, a plurality of first resistances, a first current source, a second current source, a second output node pair, a third output node pair and a switch circuit. A differential signal supplied to the input node pair is amplified with a predetermined gain (first gain) and output from the second output node pair. The differential signal is also amplified with a gain (second gain) corresponding to the resistance value between one interconnection node and another interconnection node, among the interconnection nodes connecting the plurality of first resistances, connected to the third output node pair via the switch circuit, and output from the third output node pair. The second gain can be changed by changing the two interconnection nodes connected to the third output node pair via the switch circuit.

Claims20

Dependent claims

A variable gain amplifier comprising:

an input node pair receiving a differential signal;
a first output node pair;
a voltage-current converter for outputting a differential current corresponding to a voltage between one and the other of the input node pair to the first output node pair;
a plurality of first resistances connected in series between one and the other of the first output node pair;
a first current source connected between a power supply node receiving the supply voltage and one of the first output node pair;
a second current source connected between the power supply node and the other of the first output node pair;
a second output node pair receiving a voltage at the first output node pair;
a third output node pair;
and
a switch circuit for connecting an interconnection node among interconnection nodes connecting the plurality of first resistances to one of the third output node pair and connecting another interconnection node among the interconnection nodes connecting the plurality of first resistances to the other of the third output node pair.

7 more elements

A variable gain amplifier comprising:

an input node pair receiving a differential signal;
a first output node pair;
a voltage-current converter for outputting a differential current corresponding to a voltage between one and the other of the input node pair to the first output node pair;
a plurality of first resistances connected in series between one and the other of the first output node pair;
a first current source connected between a power supply node receiving the supply voltage and one of the first output node pair;
a second current source connected between the power supply node and the other of the first output node pair;
a second output node pair receiving a voltage at the first output node pair;
a plurality of third output node pairs;
and
a plurality of switch circuits placed to correspond to the plurality of third output node pairs,
wherein each of the plurality of switch circuits connects one of the corresponding third output node pair to an interconnection node among interconnection nodes connecting the plurality of first resistances and connects the other of the corresponding third output node pair to another interconnection node among the interconnection nodes connecting the plurality of first resistances.

8 more elements

Dependencies are inferred from the claim text.

Variable gain amplifier and filter circuit

Life of this patent

Variable gain amplifier and filter circuit

Life of this patent

Abstract

Claims20