VARIABLE RESISTOR, FILTER, VARIABLE GAIN AMPLIFIER AND INTEGRATED CIRCUIT USING THE VARIABLE RESISTOR

• US 20090039955A1
• Filed: 08/06/2008
• Published: 02/12/2009
• Est. Priority Date: 08/09/2007
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Hosoya, Masahiro
• Granted Patent: US 7,750,716 B2
• Time in Patent Office: Days
• US Class Current: 327/553
• CPC Class Codes: H03H 11/1291 Current or voltage controlled filters
• CPC Class Codes: H03H 7/24 Frequency- independent attenuators

Abstract

A variable resistor formed on a silicon substrate, and changing a resistance value between an input terminal and an output terminal, includes a plurality of first resistors each having one end connected in common to the input terminal, and each having other end, a plurality of second resistors each having a resistance value smaller than the first resistors, and each having one end connected to the other end of any one of the first resistors, and a switch group interposed between the input terminal and the output terminal, and selecting one from the first resistors, and further, selecting at least one from the second resistors connected to the other end of the selected first resistor.

Claims

1. A variable resistor formed on a silicon substrate, and changing a resistance value between an input terminal and an output terminal, comprising:

a plurality of first resistors each having one end connected in common to the input terminal, and each having other end;

a plurality of second resistors each having a resistance value smaller than the first resistors, and each having one end connected to the other end of any one of the first resistors; and

a switch group interposed between the input terminal and the output terminal, and selecting one from the first resistors, and further, selecting at least one from the second resistors connected to the other end of the selected first resistor.

2. The variable resistor according to claim 1, wherein the switch group includes a plurality of switches connected in series to each of the second resistors so that turn on/off is controlled by a control signal.

3. The variable resistor according to claim 1, wherein the switch group includes a plurality of first switches connected in series to each of the second resistors so that turn on/off is controlled by a control signal, and a plurality of second switches connected in series to each of the first resistors so that turn on/off is controlled by the control signal.

4. The variable resistor according to claim 1, wherein each resistance value of the first resistors is different, and each resistance value of the first resistors and second resistors is set so that when the switch group switches the selection of the first resistors so as to increase the resistance value, sum of a resistance value of the selected first resistor by the switch group and a resistance value of the selected second resistor by the switch group increases without relation to the selection of the second resistors.

9. An active filter including:

an operational amplifier;

the variable resistor according to claim 1 connected to the operational amplifier; and

a capacitor connected to the operational amplifier.

10. A variable gain amplifier including:

an operational amplifier; and

the variable resistor according to claim 1 connected to the operational amplifier.

11. An integrated circuit including the variable resistor according to claim 1.

5. A variable resistor formed on a silicon substrate, and changing a resistance value between an input terminal and an output terminal, comprising:

a first resistor having one end connected to the input terminal, and having other end;

a plurality of second resistors each having one end connected in common to the other end of the first resistor, and each having other end;

a plurality of third resistors each having a resistance value smaller than the second resistors, and each having one end connected to the other end of any one of the second resistors; and

a switch group interposed between the other end of the first resistor and the output terminal, and selecting one from the second resistors, and further, selecting at least one from the third resistors connected to the other end of the selected second resistor.

6. The variable resistor according to claim 5, wherein the switch group includes a plurality of switches connected in series to each of the third resistors so that turn on/off is controlled by a control signal.

7. The variable resistor according to claim 5, wherein the switch group includes a plurality of first switches connected in series to each of the third resistors so that turn on/off is controlled by a control signal, and a plurality of second switches connected in series to each of the second resistors so that turn on/off is controlled by the control signal.

8. The variable resistor according to claim 5, wherein each resistance value of the second resistors is different, and each resistance value of the second resistors and third resistors is set so that when the switch group switches the selection of the second resistors so as to increase the resistance value, sum of a resistance value of the selected second resistor by the switch group and a resistance value of the selected third resistor by the switch group increases without relation to the selection of the third resistors.