# US 2017/0285058 A1 · Circuits and methods for artifact elimination

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- Number: US 2017/0285058 A1
- Document ID: US20170285058A1
- Status: Published application
- Kind: A1
- Application number: 15/623,687
- Filed: 2017-06-15
- Published: 2017-10-05
- Earliest claimed: 2005-08-30
- Assignees: Georgia Tech Research Corporation
- Applicants: Georgia Tech Research Corporation
- Inventors: Edgar A. Brown; James D. Ross; Richard A. Blum; Stephen P. DeWeerth
- Web page: https://patentgrep.com/patent/US20170285058A1

## CPC

- G01N 37/00: Details not covered by any other group of this subclass
- A61B 5/24: Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B 5/7217: {of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker}
- A61N 1/3605: {Implantable neurostimulators for stimulating central or peripheral nerve system}
- G01N 33/4836: {using multielectrode arrays}
- A61N 1/3704: {Circuits specially adapted therefor, e.g. for sensitivity control}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B)

## Abstract

Disclosed are apparatus and methods that provide the ability to electrical stimulate a physical system, and actively eliminate interference with signal acquisition (artifacts) that arises from the stimulation. The technique implemented in the circuits and methods for eliminating interference connects a discharge path to a physical interface to the system to remove charge that is built-up during stimulation. By placing the discharge path in a feedback loop that includes a recording preamplifier and AC-coupling circuitry, the physical interface is brought back to its pre-stimulation offset voltage. The disclosed apparatus and methods may be used with piezoelectric transducers, ultrasound devices, optical diodes, and polarizable and non-polarizable electrodes. The disclosed apparatus can be employed in implantable devices, in vitro or in vivo setups with vertebrate and invertebrate neural tissue, muscle fibers, pancreatic islet cells, osteoblasts, osteoclasts, bacteria, algae, fungi, protists, and plants.

## Claims

### Claim at position 1

1-20. (canceled)

### Claim 21

An apparatus comprising:
an excitation circuitry that electrically excites a physical system by applying an excitation signal to a physical interface to the physical system; and
signal acquisition circuitry that actively eliminates interference arising from the excitation signal, said signal acquisition circuitry comprises a feedback loop that incorporates the physical interface, the feedback loop further providing an electrical discharge path for the physical interface, wherein said feedback loop eliminates interference arising from the excitation of the physical system by a continuous-time adjustment of an electrical characteristic of the physical interface wherein said adjustment of the electrical characteristic is a function of a present condition and a pre-excitation condition of the physical interface.

### Claim 22 (depends on 21)

The apparatus of claim 21, wherein the signal acquisition circuitry further comprises an amplifier that is AC coupled to the physical interface.

### Claim 23 (depends on 21)

The apparatus of claim 21, which is embodied in an integrated circuit.

### Claim 24 (depends on 21)

The apparatus of claim 21, wherein the physical interface is selected from a group including piezoelectric transducers, ultrasound devices, optical diodes, polarizable and nonpolarizable electrodes.

### Claim 25 (depends on 21)

The apparatus of claim 21, wherein the interference is actively eliminated by monitoring and discharging the physical interface to a value substantially equal to the pre-excitation condition of the physical interface.

### Claim 26 (depends on 21)

The apparatus of claim 21, which is incorporated into an implantable medical device.

### Claim 27 (depends on 21)

The apparatus of claim 21, wherein the signal acquisition circuitry further comprises discharge circuitry that actively eliminates interference by transiently increasing the tracking speed of a recording amplifier in the feedback loop.

### Claim 28 (depends on 27)

The apparatus of claim 27, wherein the tracking speed of the recording amplifier is transiently increased by increasing a dominant high-pass pole of the recording amplifier.

### Claim 29 (depends on 27)

The apparatus of claim 27, wherein increasing the tracking speed is accomplished by adjusting a bias current in the recording amplifier.

### Claim 30 (depends on 29)

The apparatus of claim 29, wherein the bias current is adjusted by transiently adjusting a voltage level applied to a transconductance device that provides current that contributes to the bias current level.

### Claim 31 (depends on 29)

The apparatus of claim 29, wherein the bias current is adjusted by selectively switching on or off a switch that provides current that contributes to the bias current level.

### Claim 32 (depends on 29)

The apparatus of claim 29, wherein the bias current is adjusted by transiently adjusting a voltage level applied to a first transconductance device that provides current that contributes to the bias current level and by selectively switching on or off a second transconductance device that provides current that contributes to the bias current level.

### Claim 33 (depends on 21)

The apparatus of claim 21, wherein the signal acquisition circuitry further comprises a discharge path comprising an additional feedback loop that simulates a negative impedance that reduces the discharge time of the physical interface.

### Claim 34 (depends on 33)

The apparatus of claim 33, wherein the additional feedback loop comprises a variable resistor.

### Claim 35 (depends on 34)

The apparatus of claim 34, wherein the variable resistor provides positive feedback to the discharge path.

### Claim 36 (depends on 35)

The apparatus of claim 35, wherein the variable resistor provides positive feedback to the discharge path through a capacitor.

### Claim 37 (depends on 34)

The apparatus of claim 34, wherein the variable resistor comprises an amplifier.

### Claim 38 (depends on 34)

The apparatus of claim 34, wherein a scaled copy of discharge current from a discharge amplifier in the feedback loop is provided to the variable resistor.

### Claim 39 (depends on 33)

The apparatus of claim 33, wherein the signal acquisition circuitry further comprises discharge circuitry that actively eliminates interference by transiently increasing the tracking speed of a recording amplifier in the feedback loop.

### Claim 40 (depends on 39)

The apparatus of claim 39, wherein increasing the tracking speed is accomplished by adjusting a bias current in the recording amplifier.