Device for measuring impedance of biologic tissues including an alternating current (AC) coupled voltage-to-current converter

摘要

A device for measuring impedance of biological tissue may include electrodes and a voltage-to-current converter coupled to the electrodes to drive an alternating current (AC) through the tissue and sense an AC voltage. The converter may include an amplifier having first and second inputs and an output, a first voltage divider coupled to the first input, a second voltage divider coupled to the second input, a filter capacitor coupled between the output and the second voltage divider, a current limiting resistor coupled between the second input the second voltage divider, and a bypass capacitor coupled to the second input of the amplifier and in parallel with the resistor. A single-ended amplitude modulation (AM) demodulator may demodulate the AC voltage and generate a corresponding baseband voltage representing the impedance. The device may also include an output circuit to generate output signals representative of DC and AC components of the baseband voltage.

主权项

1. A device for measuring impedance of biological tissue comprising:
a first pair of electrodes for contacting the biological tissue; a voltage-to-current converter coupled to the first pair of electrodes and configured to drive an alternating current (AC) through the biological tissue and to sense an AC voltage, said voltage-to-current converter comprising
an amplifier having first and second inputs and an output, said amplifier coupled to said first pair of electrodes,a first resistive voltage divider coupled to the first input,a second resistive voltage divider coupled to the second input,a direct current (DC) filter capacitor coupled between the output of said amplifier and said second resistive voltage divider,a current limiting resistor coupled between the second input of said amplifier and said second resistive voltage divider, anda bypass capacitor coupled to the second input of said amplifier and in parallel with said current limiting resistor; at least one single-ended amplitude modulation (AM) demodulator configured to demodulate the AC voltage and to generate a corresponding baseband voltage representing the impedance; and an output circuit configured to generate output signals representative of DC and AC components of the baseband voltage.