US-12622624-B2 - Acquisition device to limit leakage current in electrophysiological signal recording devices

US12622624B2US 12622624 B2US12622624 B2US 12622624B2US-12622624-B2

Abstract

The device limits the leakage current in an electronic system for recording electrophysiological signals, where the transducer element is an active device, the device comprising an active transducer ( 1 ), intended to contact a human tissue, connected to a transimpedance amplifier ( 2 ), and a first resistor ( 6 ) connected parallel to the transimpedance amplifier ( 2 ), an alternate voltage source ( 7 ) and a direct voltage source ( 8 ), both connected to the active transducer ( 1 ), a first capacitor ( 3 ) connected between the alternate voltage source ( 7 ) and the active transducer ( 1 ), a second resistor ( 4 ) connected between the direct voltage source ( 8 ) and the active transducer ( 1 ), parallel with the first capacitor ( 3 ) and the alternate voltage source ( 7 ), and a second capacitor ( 5 ), connected between the active transducer ( 1 ) and the transimpedance amplifier ( 2 ).

Inventors

Antón Guimera Brunet
Lucía Re Blanco
Eduard MASVIDAL CODINA
Rosa Villa Sanz
Xavier ILLA VILA
José Antonio GARRIDO ARIZA
Nathan SCHAEFER
Ramón García Cortadella

Assignees

CONSEJO SUPERIOR DE INVESTIGACIONES CIENTÍFICAS
CONSORCIO CENTRO DE INVESTIGACION BIOMEDICA EN RED, M.P.
ICREA
INSTITUT CATALÀ DE NANOCIÈNCIA I NANOTECNOLOGIA (ICN2)

Dates

Publication Date: 20260512
Application Date: 20210917
Priority Date: 20200917

Claims (7)

1 . An acquisition device to limit leakage current in electrophysiological signal recording devices, the acquisition device comprising: a first active transducer connected to a first transimpedance amplifier and intended to contact a body tissue; an alternate voltage source connected to the first active transducer and is opposite to the first transimpedance amplifier; a direct voltage source connected to the first active transducer, parallel to the alternate voltage source; a first capacitor connected between the alternate voltage source and the first active transducer; a first resistor connected between the direct voltage source and the first active transducer, parallel to the first capacitor and the alternate voltage source; and a second capacitor connected between the first active transducer and the first transimpedance amplifier.
2 . The device according to claim 1 , wherein the first active transducer is a graphene transistor (gSGFET).
3 . The device according to claim 1 , wherein the resistance of the first resistor is higher than Vsupp/50 uA, being Vsupp a maximum supply voltage of the direct voltage source.
4 . A multiple active transducer acquisition device comprising: an acquisition device, the acquisition device comprising: a first active transducer connected to a first transimpedance amplifier and intended to contact a body tissue; an alternate voltage source connected to the first active transducer and is opposite to the first transimpedance amplifier; a direct voltage source connected to the first active transducer, parallel to the alternate voltage source; a first capacitor connected between the alternate voltage source and the first active transducer; a first resistor connected between the direct voltage source and the first active transducer, parallel to the first capacitor and the alternate voltage source; and a second capacitor connected between the first active transducer and first the transimpedance amplifier; and one or more acquisition modules, each of the one or more acquisition modules comprising: a second active transducer; a third capacitor connected to the second active transducer; a second transimpedance amplifier connected to the third capacitor; and a second resistor connected in parallel with the second transimpedance amplifier; and wherein the second active transducer of each acquisition module is connected parallel with the first active transducer of the acquisition device opposite to the third capacitor.
5 . The device according to claim 4 , wherein the first active transducer and the second active transducer are graphene transistors (gSGFET).
6 . A multiplexed array acquisition device comprising: “m×n” active transducers situated in each “m×n” position of a matrix with “m” columns and “n” rows; m common first capacitors; m common first resistors; m common alternate voltage sources; and m common direct voltage sources; wherein each common first resistor is connected in parallel to each common first capacitor, and each common first capacitor is connected to each common alternate voltage source and each common first resistor is connected to each common direct voltage source; n common second capacitors; n common transimpedance amplifiers; and n common second resistors; wherein each common second capacitor is connected to each common transimpedance amplifier and each common second resistor is connected parallel to each common transimpedance amplifier; and wherein: the active transducers situated in each column of the matrix are connected to each common first capacitor and each common first resistor, and the active transducers situated in each row of the matrix are connected to each common second capacitor.
7 . The device according to claim 6 , wherein the active transducers are graphene transistors (gSGFET).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY This patent application claims priority from PCT Application No. PCT/EP2021/075616 filed Sep. 17, 2021, which claims priority from European Patent Application No. 20382819.9 filed Sep. 17, 2020. Each of these patent applications are herein incorporated by reference in their entirety. OBJECT OF THE INVENTION The invention relates to an acquisition device that limits the leakage current in an electronic system for recording electrophysiological signals where the transducer element is an active device. BACKGROUND OF THE INVENTION The limitation of the leakage currents through a patient in electrophysiology signal recording devices is needed to meet with the regulatory laws applied to medical devices (IEC60601), and therefore for the use of the active transducers in clinical applications. Most of the systems used for recording neural signals are based on electrodes as transducer element. In these systems, neural signal acquisition is based on the amplification of the electrode's voltage, so the acquisition electronic system basically consists on a voltage amplifier with a high input impedance. FIG. 1 shows a schematic of an acquisition system based on electrodes, where measured voltage is controlled by the effective electrode impedance (Zelectrode) and the effective input impedance (Zin). Unlike these systems, acquisition systems based on active elements need to perform two functions: 1) to polarize the transducer device at an optimal working point, and 2) to amplify the signal proportional to the neural activity recorded by the transducer. FIG. 2 shows a schematic of an acquisition system based on active transducer (gSGFET) represented on the left. Vdrain and Vsource voltage sources fix the bias point, and the transimpedance amplifier, represented on the centre of the figure, amplifies the transistor current (Ids) which contains the neural signal, which is them processed. The use of active transducers, specifically ones based on graphene transistors (gSGFETs), have shown several advantages with respect to current technologies based on metal electrodes such as their ability to record very low frequency signals (<0.1 Hz) or the implementation of multiplexed interfaces to reduce connectivity. Document WO2020025786A1 describes an apparatus and method using no switching elements for multiplexing and reading arrays of sensors whose electrical resistance is modulated by the signals to be measured. Sensor elements are arranged in group and columns where each column is fed with a continuous voltage waveform of different amplitude, frequency and phase characteristics which then produce current signals that are modulated by the variable resistance signals to be measured. Modulated currents are summed row-wise and collected at the read-out circuits, either by applying a constant voltage to each row of the array or by connecting a capacitor and converting these current summations into output voltage signals. The read-out circuits de-multiplex each individual sensor signal to be measured by means of lock-in demodulation according to the frequencies and phases employed for the stimulation of each column. Document WO2020094898A1 describes flexible matrices of graphene field effects transistors with epicortical and intracortical configurations, which can register infra-slow signals and signals in a bandwidth that is typical of local field potentials. The invention is based on the graphene transistor system for measuring electrophysiological signals, comprising a processing unit and at least one graphene transistor with the graphene as the channel material contacted via two terminals, to which a variable voltage source is joined at the drain and source terminals of the transistor, with a reference as a gate terminal, and at least one filter for acquiring and dividing the signal of the transistor into at least two frequency bands, low and high, in which the first and second signals are amplified respectively with a gain value. Currently, these devices require a DC coupling operation to fix the optimal bias point. This fact limits the compliance with IEC60601-1 regulation applicable to medical equipment, which limits maximum low frequency (DC) leakage current through a patient. This leakage current must be less than 10 μA in normal operation and less than 50 μA in case of simple failure. During a normal operation, the leakage current is controlled by the gSGFET gate impedance, being in the range of 1 nA (3 orders of magnitude below the minimum stablished by the regulation). However, in the case of simple failure (i.e. bias voltage exceeds the potential windows of gSGFET due to an electronics breakdown), the leakage current is not limited by any passive electronic component. DESCRIPTION OF THE INVENTION The present invention defines a device that limits the leakage current and at the same time allows the bias point control on electrophysiological signal recording systems, prefer