Sensor with Movable Part and Biasing

• US 20120217171A1
• Filed: 02/25/2011
• Published: 08/30/2012
• Est. Priority Date: 02/25/2011
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Ceballos, Jose Luis, Wurzinger, Christoph Bernhard
• Granted Patent: US 9,525,925 B2
• Time in Patent Office: Days
• US Class Current: 205/775
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: H03F 2200/03 the amplifier being designed for audio applications
• CPC Class Codes: H03F 2203/45112 the biasing of the differential amplifier being controlled from the input or the output signal
• CPC Class Codes: H03F 2203/45116 Feedback coupled to the input of the differential amplifier
• CPC Class Codes: H03F 2203/45544 the IC comprising one or more capacitors, e.g. coupling capacitors
• CPC Class Codes: H03F 3/183 with semiconductor devices only
• CPC Class Codes: H03F 3/45071 with semiconductor devices only
• CPC Class Codes: H04R 1/04 Structural association of microphone with electric circuitry therefor in deaf-aid sets H04R25/00
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones

Abstract

Methods and apparatuses are provided wherein a sensor which comprises at least two electrodes and a movable part is alternately biased with at least two different voltages.

Claims

1. An apparatus, comprising:

a sensor comprising a movable part and at least two electrodes; and

biasing circuitry configured to alternately apply at least one first voltage and at least one second voltage to said sensor.

2. The apparatus of claim 1, wherein said biasing circuitry is configured to alternately apply said at least one first voltage and at least one second voltage to one of said movable part and said at least two electrodes.

3. The apparatus of claim 1, wherein applying said at least one first voltage is associated with a stable state of said movable part and applying said at least one second voltage is associated with an unstable state of said movable part.

4. The apparatus of claim 1, further comprising a feedback path from an output of said sensor to said biasing circuitry, said biasing circuitry being configured to provide said at least first voltage and said at least one second voltage depending on a signal received via the feedback path.

5. The apparatus of claim 1, wherein said sensor comprises at least one of a microphone, an accelerometer or a gyroscope.

6. The apparatus of claim 1, wherein said sensor is implemented as a microelectromechanical system.

7. The apparatus of claim 1, wherein said at least two electrodes comprise a first plate and a second plate, and wherein said movable part comprises a membrane suspended between said first plate and said second plate.

8. An apparatus, comprising:

a sensor comprising a first electrode, a movable part and a second electrode, a first capacitance being defined between said first electrode and said movable part and a second capacitance being defined between said movable part and said second electrode,

a first voltage source,

a first switch coupling said first voltage source with one of said movable part or said first and second electrodes, and

a second switch coupling said second voltage source with one of said movable part or said first and second electrodes.

9. The apparatus of claim 8, further comprising at least one clock coupled to said first switch and said second switch and configured to alternately close said first switch and said second switch.

10. The apparatus of claim 8, further comprising an amplifier, a first input of said amplifier being coupled to said first electrode and a second input of said amplifier being coupled to said second electrode, a first output of said amplifier being coupled to a first output pin and a second output of said amplifier being coupled to a second output pin.

11. The apparatus of claim 10, further comprising at least one further switch coupled in parallel to said amplifier, said at least one further switch being configured to be operated synchronously with said second switch.

12. The apparatus of claim 10, further comprising at least one third capacitance being coupled in parallel with said amplifier.

13. The apparatus of claim 8, further comprising biasing circuitry coupled with said first electrode and said second electrode.

14. An apparatus, comprising:

a sensor comprising a first electrode, a second electrode and a movable part arranged between said first electrode and said second electrode,

a first amplifier arrangement, wherein a first input of said first amplifier arrangement is coupled with said first electrode,

a second amplifier arrangement, a first input of said second amplifier arrangement being coupled with said second electrode and

a feedback loop coupled between outputs of said first amplifier arrangement and second amplifier arrangement and second inputs of said first amplifier arrangement and said second amplifier arrangement via a coupling.

15. The apparatus of claim 14, wherein said feedback loop comprises a further coupling between said outputs of said first amplifier arrangement and said second amplifier arrangement and said first inputs of said first amplifier arrangement and said second amplifier arrangement.

16. The apparatus of claim 15, wherein said further coupling is a coupling via capacitances.

17. The apparatus of claim 15, wherein said feedback path comprises a third amplifier arrangement configured to amplify a first signal provided via said coupling and a fourth amplifier arrangement to amplify a second signal provided via said further coupling, an amplification factor of said fourth amplifier arrangement being greater than an amplification factor of said third amplifier arrangement.

18. The apparatus of claim 17, wherein said amplification factor of said fourth amplifier arrangement is essentially twice an amplification factor of said third amplifier arrangement.

19. The apparatus of claim 14, wherein the feedback path comprises a differential difference amplifier arrangement, inputs of said differential difference amplifier arrangement being coupled with said outputs of said first amplifier arrangement and said second amplifier arrangement.

20. The apparatus of claim 14, wherein said feedback path comprises switching circuitry configured to intermittently exchange a first feedback signal and a second feedback signal in said feedback path.

21. A method, comprising:

providing a sensor comprising a movable part arranged between at least two electrodes, and

alternately switching a biasing voltage for said sensor between at least two different values.

22. The method of claim 21, wherein said switching of said biasing voltage comprises switching said sensor between a stable state and an unstable state.

23. The method of claim 21, further comprising providing said at least two different voltages depending on an output of said sensor.

24. The method of claim 21, further comprising generating a first feedback signal based on said sensor output with a first amplification and generating a second feedback signal based on said sensor output with a second amplification different from said first amplification.

25. The method of claim 21, wherein said sensor comprises at least one of a microphone, an accelerometer and a gyroscope.