Detection device, sensor, and electronic instrument

• US 20080111625A1
• Filed: 11/08/2007
• Published: 05/15/2008
• Est. Priority Date: 11/10/2006
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Fukuzawa, Akihiro
• Granted Patent: US 7,845,227 B2
• Time in Patent Office: Days
• US Class Current: 330/254
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719
• CPC Class Codes: G01C 19/5649 Signal processing
• CPC Class Codes: H03F 3/45 Differential amplifiers differential sense amplifiers G11C7/062

Abstract

A detection device includes a detection circuit. The detection circuit includes an amplifier circuit, a synchronous detection circuit, and a filter section. The amplifier circuit includes a first-type operational amplifier, and the filter section includes a second-type operational amplifier. When a channel width and a channel length of a differential-stage transistor of a differential section of the first-type operational amplifier are respectively referred to as W1a and L1a, a bias current flowing through the differential section is referred to as Ia, a channel width and a channel length of a differential-stage transistor of a differential section of the second-type operational amplifier are respectively referred to as W1b and L1b, and a bias current flowing through the differential section is referred to as Ib, W1b×L1b>W1a×L1a and Ia>Ib are satisfied.

Claims

1. A detection device comprising:

a detection circuit that receives a detection signal from a physical quantity transducer driven using a driving signal, and detects a desired signal from the detection signal, the detection circuit including;

an amplifier circuit that amplifies the detection signal from the physical quantity transducer;

a synchronous detection circuit that synchronously detects the signal amplified by the amplifier circuit; and

a filter section provided in a subsequent stage of the synchronous detection circuit;

the amplifier circuit including a first-type operational amplifier;

the filter section including a second-type operational amplifier; and

when a channel width and a channel length of a differential-stage transistor of a differential section of the first-type operational amplifier are respectively referred to as W1a and L1a, a bias current flowing through the differential section of the first-type operational amplifier is referred to as Ia, a channel width and a channel length of a differential-stage transistor of a differential section of the second-type operational amplifier are respectively referred to as W1b and L1b, and a bias current flowing through the differential section of the second-type operational amplifier is referred to as Ib, W1b×

L1b>

W1a×

L1a and Ia>

Ib being satisfied.

2. The detection device as defined in claim 1,

when a frequency of a carrier signal is referred to as f1, a frequency of the desired signal carried by the carrier signal is referred to as f2, and a corner frequency of flicker noise and thermal noise in frequency-noise characteristics is referred to as fcr, the first-type operational amplifier satisfying f1−

fcr<

fcr−

f2, and the second-type operational amplifier satisfying fcr−

f2<

f1−

fcr.

3. The detection device as defined in claim 1,

the amplifier circuit including:

first and second charge/voltage conversion circuits or first and second current/voltage conversion circuits that respectively amplify first and second detection signals from the physical quantity transducer; and

a differential amplifier circuit that differentially amplifies first and second output signals from the first and second charge/voltage conversion circuits or the first and second current/voltage conversion circuits; and

the first and second charge/voltage conversion circuits or the first and second current/voltage conversion circuits and the differential amplifier circuit including the first-type operational amplifier.

4. The detection device as defined in claim 1,

the detection circuit including a sensitivity adjustment circuit that is provided in a preceding stage of the synchronous detection circuit and adjusts sensitivity by variably controlling a gain;

and

the sensitivity adjustment circuit including the first-type operational amplifier.

5. The detection device as defined in claim 4,

the sensitivity adjustment circuit operating as a programmable-gain amplifier and a high-pass filter.

6. The detection device as defined in claim 5,

the first-type operational amplifier being used in common by the high-pass filter as an active filter and the programmable-gain amplifier.

7. The detection device as defined in claim 1,

the filter section including:

a discrete-time filter; and

a continuous-time filter provided in a preceding stage of the discrete-time filter; and

the discrete-time filter including the second-type operational amplifier.

8. The detection device as defined in claim 7,

the physical quantity transducer being a vibrator that is caused to produce vibrations using a driving signal;

and

the discrete-time filter having frequency characteristics for removing a component having a detuning frequency Δ

f−

|fd−

fs| corresponding to a difference between a driving-side resonance frequency fd and a detection-side resonance frequency fs of the vibrator and allowing a frequency component of the desired signal to pass through.

9. The detection device as defined in claim 8,

the continuous-time filter including the second-type operational amplifier;

and

the continuous-time filter having frequency characteristics for attenuating amplitude of an unnecessary signal which appears in a frequency band of a frequency k×

fd (k is a positive integer) due to synchronous detection by the synchronous detection circuit to a value equal to or smaller than amplitude of the desired signal.

10. The detection device as defined in claim 1,

the synchronous detection circuit including a third-type operational amplifier;

and

when a channel width and a channel length of a differential-stage transistor of a differential section of the third-type operational amplifier are respectively referred to as W1c and L1c and a bias current which flows through the differential section of the third-type operational amplifier is referred to as Ic, W1c×

L1c>

W1a×

L1a and Ic>

Ib being satisfied.

11. The analog circuit as defined in claim 1, further comprising:

a reference voltage supply circuit that supplies an analog reference voltage to the detection circuit;

the reference voltage supply circuit including;

a first supply circuit that includes a reference-voltage first-type operational amplifier and supplies the analog reference voltage to the amplifier circuit; and

a second supply circuit that includes a reference-voltage second-type operational amplifier and supplies the analog reference voltage to the filter section; and

when a channel width and a channel length of a differential-stage transistor of a differential section of the reference-voltage first-type operational amplifier are respectively referred to as W1d and L1d, a bias current flowing through the differential section of the reference-voltage first-type operational amplifier is referred to as Id, a channel width and a channel length of a differential-stage transistor of a differential section of the reference-voltage second-type operational amplifier are respectively referred to as W1e and L1e, and a bias current flowing through the differential section of the reference-voltage second-type operational amplifier is referred to as Ie, W1e×

L1e>

W1d×

L1d and Id>

Ie being satisfied.

15. The detection device as defined in claim 1,

the physical quantity transducer being a vibrator that is caused to produce vibrations using a driving signal.

17. A sensor comprising:

the detection device as defined in claim 1; and

the physical quantity transducer.

19. An electronic instrument comprising:

the sensor as defined in claim 17; and

a processing section that performs processes based on detection information of the sensor.

12. A detection device comprising:

a detection circuit that receives a detection signal from a physical quantity transducer driven using a driving signal, and detects a desired signal from the detection signal, the detection circuit including;

an amplifier circuit that amplifies the detection signal from the physical quantity transducer;

a synchronous detection circuit that synchronously detects the signal amplified by the amplifier circuit; and

a filter section provided in a subsequent stage of the synchronous detection circuit;

the amplifier circuit including a first-type operational amplifier;

the filter section including a second-type operational amplifier;

the first-type operational amplifier being an operational amplifier of which thermal noise at a frequency of a carrier signal is lower than that of the second-type operational amplifier; and

the second-type operational amplifier being an operational amplifier of which flicker noise at a frequency of the desired signal is lower than that of the first-type operational amplifier.

13. The detection device as defined in claim 12,

when a frequency of a carrier signal is referred to as f1, a frequency of the desired signal carried by the carrier signal is referred to as f2, and a corner frequency of flicker noise and thermal noise in frequency-noise characteristics is referred to as fcr, the first-type operational amplifier satisfying f1−

fcr<

fcr−

f2, and the second-type operational amplifier satisfying fcr−

f2<

f1−

fcr.

14. The detection device as defined in claim 12,

the synchronous detection circuit including a third-type operational amplifier;

and

the third-type operational amplifier being an operational amplifier of which thermal noise at the frequency of the carrier signal is lower than that of the second-type operational amplifier and flicker noise at the frequency of the desired signal is lower than that of the first-type operational amplifier.

16. The detection device as defined in claim 12,

the physical quantity transducer being a vibrator that is caused to produce vibrations using a driving signal.

18. A sensor comprising:

the detection device as defined in claim 12; and

the physical quantity transducer.

20. An electronic instrument comprising:

the sensor as defined in claim 18; and

a processing section that performs processes based on detection information of the sensor.