Amplifier circuit and amplifier circuit IC chip

• US 10,063,195 B2
• Filed: 06/17/2014
• Issued: 08/28/2018
• Est. Priority Date: 06/19/2013
• Status: Active Grant

• Current Assignee: Asahi Kasei Microdevices Corporation (Asahi Kasei Corporation)
• Original Assignee: Asahi Kasei Microdevices Corporation (Asahi Kasei Corporation)
• Inventors: Ogawa, Tomohiko, Koizumi, Yoshihiko
• Primary Examiner(s): Chapman, Jr., John
• Application Number:
  US14/428,480
• Publication Number:
  US 20150249434A1
• Time in Patent Office: 1,533 Days
• Field of Search: 7351433
• CPC Class Codes: G01P 15/12 by alteration of electrical resistance G01P15/0897, G01P15/105 take precedence
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 3/44 for measuring angular speed G01P3/56 takes precedence
• CPC Class Codes: G01P 3/487 delivered by rotating magnets
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H03F 2200/261 Amplifier which being suitable for instrumentation applications
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/504 the supply voltage or current being continuously controlled by a controlling signal, e.g. the controlling signal of a transistor implemented as variable resistor in a supply path for, an IC-block showed amplifier
• CPC Class Codes: H03F 2200/555 A voltage generating circuit being realised for biasing different circuit elements
• CPC Class Codes: H03F 2203/45138 Two or more differential amplifiers in IC-block form are combined, e.g. measuring amplifiers
• CPC Class Codes: H03F 2203/45336 the AAC comprising one or more resistors as feedback circuit elements
• CPC Class Codes: H03F 2203/45528 the FBC comprising one or more passive resistors and being coupled between the LC and the IC
• CPC Class Codes: H03F 2203/45591 the IC comprising one or more potentiometers
• CPC Class Codes: H03F 2203/45592 the IC comprising one or more buffer stages other than emitter or source followers between the input signal leads and input leads of the dif amp, e.g. inverter stages
• CPC Class Codes: H03F 3/45071 with semiconductor devices only
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit
• CPC Class Codes: H03F 3/45932 by using feedback means H03F3/45968 takes precedence

Abstract

An amplifier circuit includes a converter configured to convert a predefined physical quantity to a resistance value, and the resistance value converted by the converter is converted to a voltage value and then amplified. The converter includes variable resistance sensors of piezoresistance elements. A bias unit is configured to determine a bias current of the converter, and includes bias resistances. An operation amplifier unit receives, as input signals, output signals from the bias unit and the converter, and includes feedback resistances respectively connected to input and output ends of a first operational amplifier. The first operational amplifier is a whole differential operational amplifier including a common-mode feedback circuit.

Claims

1. An amplifier circuit, comprising:

a first bias unit connected to a first end of a first variable resistance sensor;

a second bias unit connected to a first end of a second variable resistance sensor, a second end of the first variable resistance sensor and a second end of the second variable resistance sensor being connected; and

an I-V converter circuit configured to convert currents output from the first end of the first variable resistance sensor and the first end of the second variable resistance sensor into voltages and output the voltages, respectively,

wherein the I-V converter circuit comprises;

a full differential operational amplifier having an inverting input terminal, a non-inverting input terminal, a non-inverting output terminal, and an inverting output terminal;

a first feedback resistance connected between the inverting input terminal and the non-inverting output terminal; and

a second feedback resistance connected between the non-inverting input terminal and the inverting output terminal, and

where the first end of the first variable resistance sensor is connected to the inverting input terminal, and

the first end of the second variable resistance sensor is connected to the non-inverting input terminal.

2. The amplifier circuit according to claim 1, further comprising a voltage control circuit configured to control the voltage at a connection point of the second end of the first variable resistance sensor and the second end of the second variable resistance sensor, so that an average value of the voltage at a first node of the first end of the first variable resistance sensor and the voltage at a second node of the second end of the second variable resistance sensor is configured to be a predefined reference voltage.

3. The amplifier circuit according to claim 2,

wherein the voltage control circuit comprises:

a current source connected to the connection point of the second end of the first variable resistance sensor and the second end of the second variable resistance sensor; and

a current control circuit configured to control a current of the current source.

4. The amplifier circuit according to claim 2, wherein the voltage control circuit comprises:

a first transistor having a drain connected to the connection point of the second end of the first variable resistance sensor and the second end of the second variable resistance sensor; and

a gate voltage control circuit configured to control a gate voltage of the first transistor.

5. The amplifier circuit according to claim 2, wherein the I-V converter circuit comprises:

a full differential operational amplifier; and

a feedback resistance configured to feedback a value of a differential output side of the full differential operational amplifier to a differential input side,

wherein a common-mode voltage of the full differential operational amplifier is same as the predefined reference voltage.

6. The amplifier circuit according to claim 1,

wherein the first bias unit is a first bias resistance, and

wherein the second bias unit is a second bias resistance.

7. The amplifier circuit according to claim 6, wherein the first bias resistance, the second bias resistance, and the feedback resistance are resistance elements made of an identical material.

8. The amplifier circuit according to claim 6,

wherein a first end of the first bias resistance is connected to the first end of the first variable resistance sensor,

wherein a first end of the second bias resistance is connected to the first end of the second variable resistance sensor,

wherein a second end of the first bias resistance is connected to the second end of the second bias resistance, and

wherein a first voltage is applied to the connection point of the second end of the first bias resistance and the second end of the second bias resistance.

9. The amplifier circuit according to claim 1,

wherein the first bias unit is a first current source,

wherein the second bias unit is a second current source, and

wherein the first current source and the second current source are configured to supply the currents in reverse proportion to a resistance value of a reference resistance to the first variable resistance sensor and the second variable resistance sensor, respectively.

10. The amplifier circuit according to claim 1, wherein

currents flow in the same direction through the first variable resistance sensor and the second variable resistance sensor, and

the first variable resistance sensor and the second variable resistance sensor have a characteristic of changing their resistance values in opposite directions to each other with respect to an input.

11. The amplifier circuit according to claim 1, wherein the first variable resistance sensor and the second variable resistance sensor are piezoresistance.

12. An angular velocity detection circuit, comprising the amplifier circuit according to claim 1,

wherein the first variable resistance sensor and the second variable resistance sensor change resistance values depending on an angular.

13. An acceleration detection circuit, comprising the amplifier circuit according to claim 1,

wherein the first variable resistance sensor and the second variable resistance sensor change resistance values depending on an acceleration.