Single-ended readout of a differential MEMS device
A circuit includes a first biasing voltage source, a second biasing voltage source, a first resistor device coupled between the first biasing voltage source and a first terminal of the circuit, a second resistor device coupled between the second biasing voltage source and a second terminal of the circuit, a third resistor device coupled between the second biasing voltage source and a third terminal, a first capacitor coupled between the third terminal and ground, and an amplifier having an input coupled to the second terminal and an output coupled to a circuit output.
1. A circuit comprising:
a first biasing voltage source;
a second biasing voltage source;
a first resistor device coupled between the first biasing voltage source and a first terminal of the circuit;
a second resistor device coupled between the second biasing voltage source and a second terminal of the circuit;
a third resistor device coupled between the second biasing voltage source and a third terminal;
a first capacitor coupled between the third terminal and ground;
an amplifier having an input coupled to the second terminal, and an output coupled to a circuit output; and
a microelectromechanical (MEMS) device coupled to the first terminal, the second terminal, and the third terminal.
2. The circuit of claim 1 , further comprising a positive feedback path between the output of the amplifier and the second terminal, or between the output of the amplifier and the third terminal.
3. The circuit of claim 1 , wherein the MEMS device is packaged in a first package, and the first resistor device, the second resistor device, the third resistor device, the first capacitor, and the amplifier are packaged in a second package.
4. The circuit of claim 1 , further comprising a second capacitor coupled between the output of the amplifier and the third terminal.
5. The circuit of claim 1 , further comprising a filter resistor interposed between the output of the amplifier and the circuit output, and a filter capacitor coupled between the circuit output and ground.
6. The circuit of claim 5 , further comprising a second capacitor coupled between the output of the amplifier and the third terminal.
7. The circuit of claim 5 , further comprising a second capacitor coupled between the circuit output and the third terminal.
8. The circuit of claim 5 , further comprising a second capacitor coupled between the circuit output and the second terminal.
9. A method of biasing a microelectromechanical (MEMS) device having a first terminal, a second terminal, and a third terminal, the method comprising:
applying a first biasing voltage to the first terminal through a first impedance;
applying a second biasing voltage to the second terminal through a second impedance;
applying the second biasing voltage to the third terminal through a third impedance; and
buffering a voltage at the second terminal to provide an output voltage signal.
10. The method of claim 9 , further comprising packaging the MEMS device in a first package, and packaging the first impedance, the second impedance, and the third impedance in a second package.
11. The method of claim 9 , further comprising coupling a first capacitor to the third terminal.
12. The method of claim 9 , further comprising coupling a second capacitor between a source of the output voltage signal and the third terminal.
13. The method of claim 9 , further comprising filtering the output voltage signal to provide a filtered output voltage signal.
14. The method of claim 13 , further comprising coupling a second capacitor between a source of the output voltage signal and the third terminal.
15. The method of claim 13 , further comprising coupling a second capacitor between a source of the filtered output voltage signal and the third terminal.
16. The method of claim 13 , further comprising coupling a second capacitor between a source of the filtered output voltage signal and the second terminal.
17. A circuit comprising:
a microelectromechanical (MEMS) device having a first terminal and a second terminal;
a first resistor device coupled between a first biasing voltage source and the first terminal;
a second resistor device coupled between a second biasing voltage source and the second terminal;
an amplifier having an amplifier input coupled to the second terminal, and an amplifier output;
a filter having a filter input coupled to the amplifier output, and a filter output; and
a third resistor device coupled between the second biasing voltage source and a third terminal of the MEMS device.
18. A circuit comprising:
a microelectromechanical (MEMS) device having a first terminal and a second terminal;
a first resistor device coupled between a first biasing voltage source and the first terminal;
a second resistor device coupled between a second biasing voltage source and the second terminal;
an amplifier having an amplifier input coupled to the second terminal, and an amplifier output;
a filter having a filter input coupled to the amplifier output, and a filter output; and
a third terminal of the MEMS device directly coupled to a third biasing voltage source.