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Capacitive sensor

A sensor and capacitive technology, applied in the direction of sensors, sensor parts, electrostatic transducer microphones, etc., can solve the problems of reduced sensitivity and increased noise, and achieve the effect of improving sensitivity

Inactive Publication Date: 2011-05-04
NXP BV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This results in a reduction in sensitivity which needs to be compensated by increasing the amplification factor of amplifier 4, which may result in an increase in noise

Method used

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Embodiment Construction

[0023] has been described in the background of the invention figure 1 and figure 2 .

[0024] image 3 An embodiment of the invention is shown in the schematic circuit diagram of . Use positive feedback to place the feedback capacitor 5(C f ) is connected across the amplifier, ie one plate of the feedback capacitor is connected to the non-inverting input 6 of the amplifier 4 and the other plate is connected to the non-inverting output 7 of the amplifier 4 . In alternative embodiments, a feedback capacitor may be connected between the inverting input of the amplifier and the inverting output of the amplifier. Therefore, in general, a feedback capacitor is connected between the input and output of an amplifier, where the input and output of the amplifier are of the same sign.

[0025] Other known arrangements of providing a capacitor in a feedback loop across an operational amplifier for amplifying the signal from a capacitive sensor are known, as disclosed in US applicati...

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Abstract

The present invention provides a capacitive sensor amplifier circuit, comprising: a capacitive sensor (1); a bias voltage supply (3) connected across the capacitive sensor (1) via a bias resistor (2); an operational amplifier (4) having an input connected to the capacitive sensor (1); and a feedback capacitor (5) connected between the input (6) and an output (7) of the amplifier (4), the input and output being of the same sign.

Description

technical field [0001] The invention relates to the amplification of signals from capacitive sensors. Background technique [0002] Capacitive sensors, such as condenser microphones, respond to received signals by a change in capacitance. This change in capacitance can be converted into a voltage signal by applying a bias voltage across the capacitive element of the sensor and amplifying the change in voltage across the capacitive element caused by the received signal. [0003] figure 1 The schematic circuit diagram shows the utilization with a DC reference voltage of 3(V ref ) in series with the bias resistor 2 (R bias ) to bias a capacitive microphone 1 with a static capacitance value C. Choose the value of bias resistor 2 such that the cutoff frequency of the sensor and bias resistor combination (determined by R bias C is determined by the inverse of the time constant) well below the frequency band of interest, which here is the audio frequency band. charges the cap...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04R19/04H04R3/00
CPCH03F1/38H03F3/181H04R3/00H04R19/04
Inventor 罗伯特·H·M·范费尔德温
Owner NXP BV