Capacitive interface circuit for low power sensor system
First Claim
1. A capacitive interface circuit comprising:
- a differential amplifier that amplifies a sensor signal to produce an output signal;
a sampling capacitor that stores the output signal; and
a correlated sampling circuit that reduces one or more noise components in the output signal.
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Abstract
This disclosure describes a capacitive interface circuit for a low power system. The capacitive interface circuit is configured to achieve very low noise sensing of capacitance-based transducers, such as a micro-electro-mechanical system (MEMS)-based sensor, with high resolution and low power. The capacitive interface circuit uses a differential amplifier and correlated triple sampling (CTS) to substantially eliminate, or at least reduce, kT/C noise, as well as amplifier offset and flicker (1/f) noise, from the output of the amplifier. The capacitive interface circuit may further include an output stage that reduces glitching, i.e., clock transients, in the output signal by allowing transients in the amplifier output to settle. In this manner, the circuit can be used in a low power system to produce a stable, low-noise output.
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Citations
51 Claims
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1. A capacitive interface circuit comprising:
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a differential amplifier that amplifies a sensor signal to produce an output signal; a sampling capacitor that stores the output signal; and a correlated sampling circuit that reduces one or more noise components in the output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A sensor device comprising:
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a sensor; a differential amplifier that amplifies a sensor signal received from the sensor to produce an output signal; a sampling capacitor that stores the output signal; and a correlated sampling circuit that reduces one or more noise components in the output signal. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. A method comprising:
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amplifying a differential sensor signal to produce an output signal; storing the output signal on a sampling capacitor; and applying a correlated sampling process to reduce one or more noise components in the output signal. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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51. A circuit comprising:
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means for amplifying a differential sensor signal to produce an output signal; means for storing the output signal on a sampling capacitor, and means for applying a correlated sampling process to reduces one or more noise components in the output signal.
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Specification