Abstract: A method for forming a sensor circuit. The method includes forming a plurality of magnetoresistive structures having a first predefined reference magnetization direction in a first common area of a common semiconductor substrate; forming a plurality of magnetoresistive structures having a second predefined reference magnetization direction in a second common area of the common semiconductor substrate; and forming electrically conductive structures electrically coupling the magnetoresistive structures having the first predefined reference magnetization direction to the magnetoresistive structures having the second predefined reference magnetization direction to form a plurality of half-bridge sensor circuits, wherein each half-bridge sensor circuit comprises a magnetoresistive structure having the first predefined reference magnetization direction electrically coupled to a second magnetoresistive structure having the second predefined reference magnetization direction.

Abstract: A photoacoustic detector unit comprises a housing having an opening, and also a photoacoustic transducer designed to convert optical radiation into at least one from a pressure signal or a heat signal. The photoacoustic transducer covers the opening of the housing, such that the photoacoustic transducer and the housing form an acoustically tight cavity. A pressure pick-up is arranged in the acoustically tight cavity.

Abstract: A photoacoustic detector unit comprises a housing having an opening, and also a photoacoustic transducer designed to convert optical radiation into at least one from a pressure signal or a heat signal. The photoacoustic transducer covers the opening of the housing, such that the photoacoustic transducer and the housing form an acoustically tight cavity. A pressure pick-up is arranged in the acoustically tight cavity.

Abstract: A gas sensor having a heater, a receiver, and a space arranged between the heater and the receiver, is described, the heater being configured to generate a thermoacoustic sound wave propagating through the space by using a stimulation signal. The receiver is in this case configured to receive the thermoacoustic sound wave that has propagated through the space and to convert it into a reception signal that has a time-of-flight-dependent shift with respect to the stimulation signal and therefore information relating to the gas concentration in the space.

Abstract: A photoacoustic sensor includes a first MEMS device and a second MEMS device. The first MEMS device includes a first MEMS component including an optical emitter, and a first optically transparent cover wafer-bonded to the first MEMS component, wherein the first MEMS component and the first optically transparent cover form a first closed cavity. The second MEMS device includes a second MEMS component including a pressure detector, and a second optically transparent cover wafer-bonded to the second MEMS component, wherein the second MEMS component and the second optically transparent cover form a second closed cavity.

Abstract: An apparatus for in-situ calibration of a photoacoustic sensor includes a measurement device configured to measure an electric signal at an IR emitter of the photoacoustic sensor, wherein the IR emitter generates an electromagnetic spectrum based on the electric signal; and a calibration unit including processing circuitry, configured to compare the electric signal with a comparison value to generate a comparison result used as calibration information. When performing the in-situ calibration, the calibration unit is configured to adjust the electric signal based on the calibration information, or the calibration unit is configured to process an output signal of the photoacoustic sensor based on the calibration information to obtain an adjusted output signal of the photoacoustic sensor.

Abstract: A photoacoustic sensor includes a first MEMS device and a second MEMS device. The first MEMS device includes a first MEMS component including an optical emitter, and a first optically transparent cover wafer-bonded to the first MEMS component, wherein the first MEMS component and the first optically transparent cover form a first closed cavity. The second MEMS device includes a second MEMS component including a pressure detector, and a second optically transparent cover wafer-bonded to the second MEMS component, wherein the second MEMS component and the second optically transparent cover form a second closed cavity.

Abstract: A gas sensor includes a multi-wafer stack of a plurality of layers and a measurement chamber. The plurality of layers includes a first layer comprising a sensor element that has a microelectromechanical system (MEMS) membrane; and a second layer comprising an emitter element configured to emit electromagnetic radiation. The measurement chamber is interposed between the first layer and the second layer. The measurement chamber is configured to receive a measurement gas and further receive the electromagnetic radiation emitted by the emitter element as the electromagnetic radiation travels along a radiation path from a first end of the measurement chamber to a second end of the measurement chamber that is opposite to the first end.

Abstract: A gas sensor includes a hollow space, a gas permeation structure which is arranged between the hollow space and the exterior space and contains a selectively gas-permeable element, wherein the hollow space is hermetically sealed with the exception of the gas permeation structure, and one or more sensor elements which are configured for detecting the presence of one or more gases in the hollow space.

Abstract: An apparatus for in-situ calibration of a photoacoustic sensor includes a measurement device configured to measure an electric signal at an IR emitter of the photoacoustic sensor, wherein the IR emitter generates an electromagnetic spectrum based on the electric signal; and a calibration unit including processing circuitry, configured to compare the electric signal with a comparison value to generate a comparison result used as calibration information. When performing the in-situ calibration, the calibration unit is configured to adjust the electric signal based on the calibration information, or the calibration unit is configured to process an output signal of the photoacoustic sensor based on the calibration information to obtain an adjusted output signal of the photoacoustic sensor.

Abstract: An apparatus for in-situ calibration of a photoacoustic sensor is provided. The apparatus includes a calibration unit that includes at least one processor configured to calculate calibration information. A light emitter of the photoacoustic sensor is configured to emit an electromagnetic spectrum and the photoacoustic sensor is configured to provide at least two measurement signals based on at least two electromagnetic spectra. The calibration unit is configured to compare the at least two measurement signals to obtain the calibration information and apply the calibration information to the photoacoustic sensor to perform the in-situ calibration.

Abstract: A gas sensor having a heater, a receiver, and a space arranged between the heater and the receiver, is described, the heater being configured to generate a thermoacoustic sound wave propagating through the space by using a stimulation signal. The receiver is in this case configured to receive the thermoacoustic sound wave that has propagated through the space and to convert it into a reception signal that has a time-of-flight-dependent shift with respect to the stimulation signal and therefore information relating to the gas concentration in the space.

Abstract: A photoacoustic gas sensor is provided. The photoacoustic gas sensor includes a hermetically sealed housing filled with a reference gas. Further, the photoacoustic gas sensor includes a microphone system arranged inside the housing. The microphone system is configured to generate a first microphone signal comprising a first signal component related to a photoacoustic excitation of the reference gas and a second microphone signal comprising a second signal component related to the photoacoustic excitation. The photoacoustic gas sensor additionally includes a circuit configured to generate an output signal based on the first microphone signal and the second microphone signal by destructively superimposing a third signal component of the first microphone signal related to mechanical vibrations of the photoacoustic gas sensor and a fourth signal component of the second microphone signal related to the mechanical vibrations.

Abstract: A gas sensor includes a multi-wafer stack of a plurality of layers and a measurement chamber. The plurality of layers includes a first layer comprising a sensor element that has a microelectromechanical system (MEMS) membrane; and a second layer comprising an emitter element configured to emit electromagnetic radiation. The measurement chamber is interposed between the first layer and the second layer. The measurement chamber is configured to receive a measurement gas and further receive the electromagnetic radiation emitted by the emitter element as the electromagnetic radiation travels along a radiation path from a first end of the measurement chamber to a second end of the measurement chamber that is opposite to the first end.

Abstract: A gas sensor includes a multi-wafer stack of a plurality of layers and a measurement chamber. The plurality of layers includes a first layer comprising a sensor element that has a microelectromechanical system (MEMS) membrane; and a second layer comprising an emitter element configured to emit electromagnetic radiation. The measurement chamber is interposed between the first layer and the second layer. The measurement chamber is configured to receive a measurement gas and further receive the electromagnetic radiation emitted by the emitter element as the electromagnetic radiation travels along a radiation path from a first end of the measurement chamber to a second end of the measurement chamber that is opposite to the first end.

Abstract: A photoacoustic sensor includes a first MEMS device and a second MEMS device. The first MEMS device includes a first MEMS component including an optical emitter, and a first optically transparent cover wafer-bonded to the first MEMS component, wherein the first MEMS component and the first optically transparent cover form a first closed cavity. The second MEMS device includes a second MEMS component including a pressure detector, and a second optically transparent cover wafer-bonded to the second MEMS component, wherein the second MEMS component and the second optically transparent cover form a second closed cavity.

Abstract: A photoacoustic detector unit comprises a housing having an opening, and also a photoacoustic transducer designed to convert optical radiation into at least one from a pressure signal or a heat signal. The photoacoustic transducer covers the opening of the housing, such that the photoacoustic transducer and the housing form an acoustically tight cavity. A pressure pick-up is arranged in the acoustically tight cavity.

Abstract: An apparatus containing an optical emitter configured to emit optical radiation is provided. Further, the apparatus includes a first hermetically sealed measurement cell filled with a first gas. The first gas is configured to absorb the optical radiation at least partially at one or more predetermined wavelengths. Additionally, the apparatus includes a first microphone arranged in the measurement cell and configured to generate a first microphone signal on a basis of a photoacoustic excitation of the first gas by the optical radiation. The apparatus moreover includes an evaluation circuit configured to take the first microphone signal as a basis for generating a first measurement signal indicating an emission intensity of the optical emitter at the one or more predetermined wavelengths.

Abstract: An example of a system comprises a volume filled with a gas, a gas excitation device configured to excite the gas inside the volume, a microphone configured to output a microphone signal on the basis of the gas excited by the gas excitation device, and a testing unit configured to take the microphone signal as a basis for testing a gas-tightness of the volume. An example of a photoacoustic sensor comprises a hermetically sealed sensor cell, a gas excitation device and a testing unit configured to take the microphone signal dependent on the thermally excited gas as a basis for testing a gas-tightness of the sensor cell. One example comprises a method for testing a gas-tightness of a volume filled with a gas.

Abstract: A gas sensor includes a multi-wafer stack of a plurality of layers and a measurement chamber. The plurality of layers includes a first layer comprising a sensor element that has a microelectromechanical system (MEMS) membrane; and a second layer comprising an emitter element configured to emit electromagnetic radiation. The measurement chamber is interposed between the first layer and the second layer. The measurement chamber is configured to receive a measurement gas and further receive the electromagnetic radiation emitted by the emitter element as the electromagnetic radiation travels along a radiation path from a first end of the measurement chamber to a second end of the measurement chamber that is opposite to the first end.