US 8,913,762 B2Granted

Capacitive transducer circuit and method

AssigneeWolfson Microelectronics plc

InventorsColin Findlay Steele, Goran Stojanovic, John Paul Lesso

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Abstract

A capacitive transducer circuit comprises a capacitive transducer having first and second electrodes. The first and second electrodes are biased by respective first and second bias voltages. An amplifier is connected to receive a first analog signal on an input terminal, the first analog signal being generated by the capacitive transducer, and to generate a second analog signal on an output terminal. A digital feedback circuit is connected between the output terminal of the amplifier and the input terminal of the amplifier. The digital feedback circuit is configured to provide one of said first or second bias voltages. The output of a voltage source which provides the other bias voltage for the capacitive transducer may be filtered by a low pass filter. The low pass filter may comprise a switched capacitor filter circuit.

Claims52

Dependent claims

A capacitive transducer circuit comprising:

a MEMS capacitive transducer comprising first and second electrodes, wherein the first and second electrodes are biased by respective first and second bias voltages, and wherein the capacitive transducer generates a first analogue signal;
an amplifier connected to receive the first analogue signal on an input terminal and generate a second analogue signal on an output terminal;
and
a digital feedback circuit connected between the output terminal of the amplifier and the input terminal of the amplifier, wherein the digital feedback circuit is configured to receive the second analogue signal from the output terminal of the amplifier and operatively bias the input terminal of the amplifier, wherein the digital feedback circuit comprises:
an analogue to digital converter for converting the second analogue signal into a digital signal;
a digital filter connected to receive the output of the analogue to digital converter, and output a filtered digital signal;
and
a digital to analogue converter connected to receive the filtered digital signal, and control one of said first or second bias voltages.

5 more elements

A method of operatively biasing a capacitive transducer circuit, the method comprising the steps of:

providing a MEMS capacitive transducer comprising first and second electrodes, wherein the first and second electrodes are biased by respective first and second bias voltages, and wherein the capacitive transducer generates a first analogue signal;
providing an amplifier connected to receive the first analogue signal on an input terminal and generate a second analogue signal on an output terminal;
and
providing a digital feedback circuit between the output terminal of the amplifier and the input terminal of the amplifier, wherein the digital feedback circuit comprises:
an analogue to digital converter for converting the second analogue signal into a digital signal;
a digital filter connected to receive the output of the analogue to digital converter, and output a filtered digital signal;
and
a digital to analogue converter connected to receive the filtered digital signal, and control one of said first or second bias voltages
wherein the digital feedback circuit is configured to receive the second analogue signal from the output terminal of the amplifier and operatively bias the input terminal of the amplifier.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/812,390Filed 7 May 2009
Priority: GB 0808292.77 May 2008
Published: US 2010/0315272 A116 Dec 2010
Granted: 16 Dec 2014
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G01D 5/24
Influencing the magnitude of a current or voltage: by varying capacitance
G01D 3/032
Mitigating undesired influences, e.g. temperature, pressure: affecting incoming signal, e.g. by averaging; gating undesired signals
H04R 3/00
Circuits for transducers
H04R 19/005
Electrostatic transducers: using semiconductor materials