Sensitivity Adjustment Apparatus And Method For MEMS Devices

• US 20130044898A1
• Filed: 08/16/2012
• Published: 02/21/2013
• Est. Priority Date: 08/18/2011
• Status: Active Grant

• Current Assignee: Knowles Electronics Llc (Knowles Corporation)
• Original Assignee: Knowles Electronics Llc (Knowles Corporation)
• Inventors: Schultz, Jordan T., Dai, Weiwen, Loeppert, Peter V.
• Granted Patent: US 9,635,460 B2
• Time in Patent Office: Days
• US Class Current: 381/111
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 3/06 of electrostatic transducers

Abstract

A microelectromechanical (MEMS) microphone includes a MEMS motor and a gain adjustment apparatus. The MEMS motor includes at least a diaphragm and a charge plate and is configured to receive sound energy and transform the sound energy into an electrical signal. The gain adjustment apparatus has an input and an output and is coupled to the MEMS motor. The gain adjustment apparatus is configured to receive the electrical signal from the MEMS motor at the input and adjust the gain of the electrical signal as measured from the output of the gain adjustment apparatus. The amount of gain is selected so as to obtain a favorable sensitivity for the microphone.

Claims

1. A microelectromechanical (MEMS) microphone comprising:

a MEMS motor, the MEMS motor including at least a diaphragm and a charge plate, the MEMS motor configured to receive sound energy and transform the sound energy into an electrical signal;

a gain adjustment apparatus having an input and an output and coupled to the MEMS motor, the gain adjustment apparatus configured to receive the electrical signal from the MEMS motor at the input and adjust the gain of the electrical signal as measured from the output of the gain adjustment apparatus, an amount of gain selected so as to obtain a favorable sensitivity for the microphone.

2. The MEMS microphone of claim 1 wherein the gain adjustment apparatus comprises a plurality of switchable resistors.

3. The MEMS microphone of claim 1 wherein the gain adjustment apparatus comprises a plurality of switchable capacitors.

4. The MEMS microphone of claim 1 wherein the gain adjustment apparatus comprises a plurality of switchable resistors and a plurality of switchable capacitors.

5. The MEMS microphone of claim 1 wherein the gain adjustment apparatus includes a switch to select at least one element that adjusts the gain of the electrical signal.

6. The MEMS microphone of claim 1 wherein the gain adjustment apparatus is configured to be adjusted dynamically.

7. The MEMS microphone of claim 1 wherein the gain adjustment apparatus is configured to be adjusted permanently.

8. A method of adjusting of a MEMS microphone comprising:

measuring the sensitivity of a MEMS microphone at a predetermined frequency;

when the sensitivity is unacceptable, dynamically adjusting the gain of the microphone;

subsequently measuring the sensitivity of the microphone to determine whether the measured sensitivity is acceptable.

9. The method of claim 8 wherein dynamically adjusting the gain comprises selecting at least one resistor to adjust the gain of the microphone.

10. The method of claim 8 wherein dynamically adjusting the gain comprises selecting at least one capacitor to adjust the gain of the microphone.

11. The method of claim 8 wherein dynamically adjusting the gain comprises selecting at least one resistor and at least one capacitor to adjust the gain of the microphone.

12. The method of claim 8 further comprising permanently adjusting the gain of the microphone.