Apparatus and a method for generating a sensor signal indicating information on a capacitance of a variable capacitor comprising a variable capacitance

An apparatus for generating a sensor signal indicating information on a capacitance of a variable capacitor comprising a variable capacitance, the apparatus comprising:

• the variable capacitor comprising the variable capacitance;
• a bias voltage unit configured to bias the variable capacitor by a predefined bias voltage;
• a sensor unit configured to generate a digital sensor signal and the sensor signal indicating information on a varying current flowing through a connection between the sensor unit and the variable capacitor caused by a variation of the capacitance of the variable capacitor while the variable capacitor is biased by the predefined bias voltage,
• wherein the sensor unit comprises an analog-to-digital-converter connected to an operational amplifier and configured to generate the digital sensor signal based on an analog to digital conversion of an analog sensor signal, wherein the operational amplifier of the sensor unit comprises an inverting operational amplifier with a capacitive feedback connected to an inverting input of the operational amplifier;
• and
• a compensation unit configured to provide a compensation signal to the sensor signal such that the compensation signal is processed along with the sensor signal such that nonlinear signal portions of the sensor signal are reduced,
• wherein the compensation unit is configured to calculate a compensated sensor signal based on the digital sensor signal generated by the sensor unit and provide the compensation signal to a node at an output of the sensor unit,
• wherein the variable capacitor with a variable capacitance comprises a membrane between two back plates, wherein the membrane is biased with the predefined bias voltage, wherein the sensor unit is connected to a first back plate of the variable capacitor and is configured to generate the sensor signal indicating a varying current from or to the first back plate of the variable capacitor caused by a movement of the membrane of the variable capacitor, wherein the compensation unit is connected to a second back plate of the variable capacitor and is configured to generate the compensation signal indicating a varying current from or to the second back plate of the variable capacitor caused by the movement of the membrane of the variable capacitor, wherein the second back plate of the variable capacitor is connected to an inverting input of another operational amplifier and the another operational amplifier is configured to provide the compensation signal at an output of the another operational amplifier.

An apparatus for generating a sensor signal indicating information on a capacitance of a variable capacitor comprising a variable capacitance, the apparatus comprising:

• the variable capacitor comprising the variable capacitance, wherein the variable capacitor with the variable capacitance comprises a membrane between two back plates, wherein one back plate is formed by a bottom of a cavity below the membrane;
• a bias voltage unit configured to bias the membrane of the variable capacitor by a predefined bias voltage;
• a sensor unit configured to generate a sensor signal indicating information on a varying current flowing through a connection between the sensor unit and the variable capacitor caused by a variation of the capacitance of the variable capacitor while the variable capacitor is biased by the predefined bias voltage, wherein the sensor unit comprises an inverting operational amplifier with a capacitive feedback connected to an inverting input of the operational amplifier of the sensor unit;
• and
• a compensation unit configured to provide a compensation signal to the sensor signal such that the compensation signal is processed along with the sensor signal such that nonlinear signal portions of the sensor signal are reduced, wherein the compensation unit is configured to calculate a compensated sensor signal based on a digital sensor signal generated by the sensor unit, and provide the compensation signal to the variable capacitor;
• wherein a first back plate of the variable capacitor is connected to the inverting input of the operational amplifier of the sensor unit and the operational amplifier of the sensor unit is configured to provide the sensor signal at the output of the operational amplifier of the sensor unit, wherein the compensation unit comprises an inverting operational amplifier with a capacitive feedback connected to an inverting input of the operational amplifier of the compensation unit, wherein a second back plate of the variable capacitor is connected to the inverting input of the operational amplifier of the compensation unit and the operational amplifier of the compensation unit is configured to provide the compensation signal at an output of the operational amplifier of the compensation unit.

An apparatus for generating a sensor signal indicating information on a capacitance of a variable capacitor comprising a variable capacitance, the apparatus comprising:

• the variable capacitor comprising the variable capacitance, wherein the variable capacitor with the variable capacitance comprises a membrane between two back plates, wherein one back plate is formed by a bottom of a cavity below the membrane;
• a sensor unit configured to generate a sensor signal indicating information on a varying current flowing through a connection between the sensor unit and the variable capacitor caused by a variation of the capacitance of the variable capacitor while the variable capacitor is biased by a predefined bias voltage, wherein the sensor unit comprises an inverting operational amplifier with a capacitive feedback connected to an inverting input of the operational amplifier, wherein the capacitive feedback is configured to programmably adjust a gain of the inverting operational amplifier;
• and
• a compensation unit configured to influence the sensor signal by providing a compensation signal reducing nonlinear signal portions of the sensor signal with a compensation signal, calculate a compensated sensor signal based on a digital sensor signal generated by the sensor unit and provide the compensation signal to the variable capacitor, wherein a first back plate of the variable capacitor is connected to the inverting input of the operational amplifier of the sensor unit and the operational amplifier of the sensor unit is configured to provide the sensor signal at the output of the operational amplifier of the sensor unit, wherein the compensation unit comprises an inverting operational amplifier with a capacitive feedback connected to an inverting input of the operational amplifier of the compensation unit, wherein a second back plate of the variable capacitor is connected to the inverting input of the operational amplifier of the compensation unit and the operational amplifier of the compensation unit is configured to provide the compensation signal at an output of the operational amplifier of the compensation unit.

A method for generating a sensor signal indicating information on a capacitance of a variable capacitor with a variable capacitance, the method comprising:

• generating a sensor signal indicating a varying current flowing through a connection between a sensor unit and the variable capacitor caused by a variation of the capacitance of the variable capacitor biased by a predefined bias voltage, wherein the predefined bias voltage is a constant voltage, and wherein the sensor unit comprises an inverting operational amplifier with a capacitive feedback connected to an inverting input of the operational amplifier;
• and
• influencing the sensor signal by a compensation unit by providing a compensation signal to the sensor signal directly at an output of the sensor unit such that the compensation signal is processed along with the sensor signal to reduce nonlinear signal portions of the sensor signal, wherein a first back plate of the variable capacitor is connected to the inverting input of the operational amplifier of the sensor unit and the operational amplifier of the sensor unit is configured to provide the sensor signal at the output of the operational amplifier of the sensor unit, wherein the compensation unit comprises an inverting operational amplifier with a capacitive feedback connected to an inverting input of the operational amplifier of the compensation unit, wherein a second back plate of the variable capacitor is connected to the inverting input of the operational amplifier of the compensation unit and the operational amplifier of the compensation unit is configured to provide the compensation signal at an output of the operational amplifier of the compensation unit.