Apparatus for measuring electrical impedance
First Claim
1. An apparatus for measuring electrical impedance, comprising:
- two input electrodes contacted to a subject for measuring impedance;
a difference amplifier to which two signals inputted to the two input electrodes are inputted;
a device for extracting a common mode component of the two signals inputted to the two input electrodes;
the third electrode contacted to the subject for measuring impedance;
the first multiplier to which the common mode component is inputted;
the first filter coupled with the first multiplier; and
the second multiplier coupled with the first filter;
wherein a feedback signal outputted from the second multiplier is inputted to the third electrode.
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Abstract
The present invention provides an apparatus for measuring electrical impedance comprising: two input electrodes contacted to a subject for measuring impedance; a difference amplifier to which two signals inputted to the two input electrodes are inputted; a device for extracting a common mode component of two signals inputted to the two input electrodes; the third electrode contacted to the subject for measuring impedance; the first multiplier to which the common mode component is inputted; the first filter coupled with lo the first multiplier; the second multiplier coupled with the first filter; wherein a feedback signal outputted from the second multiplier is inputted to the third electrode.
37 Citations
13 Claims
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1. An apparatus for measuring electrical impedance, comprising:
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two input electrodes contacted to a subject for measuring impedance;
a difference amplifier to which two signals inputted to the two input electrodes are inputted;
a device for extracting a common mode component of the two signals inputted to the two input electrodes;
the third electrode contacted to the subject for measuring impedance;
the first multiplier to which the common mode component is inputted;
the first filter coupled with the first multiplier; and
the second multiplier coupled with the first filter;
wherein a feedback signal outputted from the second multiplier is inputted to the third electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A preamplifier comprising:
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a voltage follower;
a wideband variable-gain gain stage coupled with the voltage follower; and
a feedback capacitor and a feedback resistor connected in series between an input terminal of the voltage follower and an output terminal of the gain stage;
wherein input impedance of the preamplifier is high.
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10. An apparatus for measuring electrical impedance comprising a preamplifier comprising:
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a voltage follower;
a wideband variable-gain gain stage coupled with the voltage follower; and
a feedback capacitor and a feedback resistor connected in series between an input terminal of the voltage follower and an output terminal of the gain stage;
wherein input impedance of the preamplifier is high. - View Dependent Claims (11, 12, 13)
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Specification