8-Channel Biphasic Current Stimulator Optimized for Retinal Prostheses

2021 ◽  
Vol 21 (8) ◽  
pp. 4298-4302
Author(s):  
Chae-Eun Lee ◽  
Younginha Jung ◽  
Yoon-Kyu Song
Keyword(s):  
Supply Voltage ◽  
Ganglion Cells ◽  
Current Source ◽  
Small Region ◽  
Cmos Process ◽  
Retinal Ganglion ◽  
Stimulation Parameter ◽  
Retinal Prostheses ◽  
Key Characteristics ◽  
High Output Impedance

Retinal prostheses substitute the functionality of damaged photoreceptors by electrically stimulating retinal ganglion cells (RGCs). RGCs, densely packed in a small region, needs a high spatial resolution of the microelectrode, which in turn raises its impedance. Therefore, the high output impedance circuit and the high compliance output voltage are the key characteristics of the current-source-based stimulator. Also, as the system is intended to implant in the retina, the stimulation parameter should be optimized for efficiency and safety. Here we designed 8-channel neural stimulator customized to the retinal ganglion cell. Designed IC is fabricated in the TSMC 0.18 μm 1P6M RF CMOS process with 3.3 V supply voltage, occupying the 1060 μm×950 μm area.

scholarly journals on and off Channels of the Frog Optic Tectum Revealed by Current Source Density Analysis

1998 ◽  
Vol 80 (4) ◽  
pp. 1886-1899 ◽  
Author(s):  
Hideki Nakagawa ◽  
Nobuyoshi Matsumoto
Keyword(s):  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Current Source ◽  
Current Source Density ◽  
Synaptic Activity ◽  
Diffuse Light ◽  
Retinal Ganglion ◽  
Source Density ◽  
Current Source Density Analysis ◽  
Density Analysis

Nakagawa, Hideki and Nobuyoshi Matsumoto. on and off channels of the frog optic tectum revealed by current source density analysis. J. Neurophysiol. 80: 1886–1899, 1998. The spatiotemporal patterns of excitatory synaptic activity in response to diffuse light on and off stimuli were examined by means of current source density (CSD) analysis. The qualitative and quantitative analyses obtained from 24 depth profiles for each stimulus revealed obviously different distributions of synaptic activity in the laminar structure. Two or three dominant current sinks I, II, and III were evoked in response to diffuse light on stimulation. Sink I was observed at the bottom of the retinorecipient layer. Both sinks II and III, showing an identical spatial pattern, were observed just above sink I. On the other hand, diffuse light off stimulation elicited up to six current sinks IV, V, VI, VII, VIII, and IX. Sink IV was observed at the bottom of the retinorecipient layer. Sink V was observed in the most superficial layer. Both sinks VI and VIII were located between the two preceding sinks. Finally, sinks VII and IX occurred below the retinorecipient layer. Five electrically evoked current sinks A, B, C, D, and E, characterized in our previous study, were also recognized in the present quantitative analysis. A statistical analysis revealed that, in visually evoked responses, statistical differences in the spatial distribution were not present between sinks I and IV, and sinks II and VIII ( P < 0.05). The analysis also showed that, in electrically evoked responses, only a pair of sinks C and E exhibit virtually identical spatial distribution ( P < 0.05). Based on well-known properties of the retinal ganglion cells, possible neuronal mechanisms underlying each of current sinks in the on and off channels and their functional meanings were considered. Sink I reflects the excitatory monosynaptic activity derived from R3 retinal ganglion cells. Sink IV reflects the excitatory monosynaptic activity derived from both R3 and R4 cells. Sinks V, VI, VII, and IX may be composed of successive polysynaptic excitatory potentials derived from convergence of inputs from both R3 and R4 cells. We concluded that the early four sinks play in particular an important role in eliciting avoidance behavior. On the other hand, sinks II, III, and VIII reflect excitatory synaptic activities derived from on-off retinal fibers of another type having slow conduction velocity. These late current sinks were suggested to mediate prey catching and its facilitation.

scholarly journals Differential stimulation of the retina with glutamate toward a neurotransmitter-based retinal prosthesis

2016 ◽  
Author(s):  
Corey M. Rountree ◽  
Samsoon Inayat ◽  
John B. Troy ◽  
Laxman Saggere
Keyword(s):  
Visual Information ◽  
Ganglion Cells ◽  
Retinal Ganglion ◽  
Retinal Prostheses ◽  
Retinal Stimulation ◽  
Stimulation Parameters ◽  
Normal Means ◽  
Retinal Pathways ◽  
Pulsatile Delivery ◽  
Stimulation Of

ABSTRACTSubretinal stimulation of the retina with neurotransmitters, the normal means of conveying visual information, is a potentially better alternative to electrical stimulation widely used in current retinal prostheses for treating blindness from photoreceptor degenerative diseases. Yet, no retinal stimulation study exploiting the inner retinal pathways exists. Here, we demonstrate the feasibility of differentially stimulating retinal ganglion cells (RGCs) through the inner nuclear layer of the retina with glutamate, a primary neurotransmitter chemical, in a biomimetic way. We show that controlled pulsatile delivery of glutamate into the subsurface of explanted wild-type rat retinas elicits highly localized simultaneous inhibitory and excitatory spike rate responses in OFF and ON RGCs. We also present the spatiotemporal characteristics of RGC responses to subretinally injected glutamate and the therapeutic stimulation parameters. Our findings could pave the way for future development of a neurotransmitter-based subretinal prosthesis offering more naturalistic vision and better visual acuity than electrical prostheses.

12-BIT PSEUDO-DIFFERENTIAL CURRENT-SOURCE RESISTOR-STRING HYBRID DAC

2011 ◽  
Vol 20 (04) ◽  
pp. 709-725 ◽  
Author(s):  
M. T. S. AB-AZIZ ◽  
A. MARZUKI ◽  
Z. A. A. AZIZ
Keyword(s):  
Supply Voltage ◽  
Current Source ◽  
Cmos Process ◽  
Least Significant Bit ◽  
Process Technology ◽  
Analog Converter ◽  
Final Design ◽  
Resistor String ◽  
Simulation Results ◽  
Binary Weighted

This paper discusses a hybrid Digital-Analog Converter (DAC) architecture which is a combination of a binary-weighted resistor approach for eight bits in the least-significant-bit and thermometer coded approach for four bits in the most-significant-bit. The proposed design combines advantages of the binary-weighted resistor approach and thermometer coded approach. The final design is composed of two 12-bit DACs to achieve a pseudo differential output signal. The converter was designed with a Silterra 0.18 μm 1.8 V/3.3 V CMOS process technology. The post-layout simulation results show that this design achieves 12-bit resolution with INL and DNL of 0.375 LSB and 0.25 LSB, respectively. The power consumption is 6.291 mW when the designed DAC is biased with supply voltage equal to 3 V. The performance is accomplished with a design area of 230 μm × 255 μm.

scholarly journals Insights from Computational Modelling: Selective Stimulation of Retinal Ganglion Cells

2020 ◽  
pp. 233-247
Author(s):  
Tianruo Guo ◽  
David Tsai ◽  
Siwei Bai ◽  
Mohit Shivdasani ◽  
Madhuvanthi Muralidharan ◽  
...  
Keyword(s):  
Retinal Ganglion Cells ◽  
Computational Models ◽  
Ganglion Cells ◽  
Computational Modelling ◽  
Retinal Ganglion ◽  
Retinal Prostheses ◽  
Differential Activation ◽  
Photoreceptor Layer ◽  
Suprachoroidal Space ◽  
Wide Range

AbstractImprovements to the efficacy of retinal neuroprostheses can be achieved by developing more sophisticated neural stimulation strategies to enable selective or differential activation of specific retinal ganglion cells (RGCs). Recent retinal studies have demonstrated the ability to differentially recruit ON and OFF RGCs – the two major information pathways of the retina – using high-frequency electrical stimulation (HFS). However, there remain many unknowns, since this is a relatively unexplored field. For example, can we achieve ON/OFF selectivity over a wide range of stimulus frequencies and amplitudes? Furthermore, existing demonstrations of HFS efficacy in retinal prostheses have been based on epiretinal placement of electrodes. Other clinically popular techniques include subretinal or suprachoroidal placement, where electrodes are located at the photoreceptor layer or in the suprachoroidal space, respectively, and these locations are quite distant from the RGC layer. Would HFS-based differential activation work from these locations? In this chapter, we conducted in silico investigations to explore the generalizability of HFS to differentially active ON and OFF RGCs. Computational models are particularly well suited for these investigations. The electric field can be accurately described by mathematical formulations, and simulated neurons can be “probed” at resolutions well beyond those achievable by today’s state-of-the-art experimental techniques.

A VERY LOW-TC SECOND-ORDER TEMPERATURE-COMPENSATED CMOS CURRENT REFERENCE

2014 ◽  
Vol 23 (03) ◽  
pp. 1450042 ◽  
Author(s):  
LIANG LIANG ◽  
ZHANGMING ZHU ◽  
YINTANG YANG
Keyword(s):  
Temperature Compensation ◽  
Supply Voltage ◽  
Design Method ◽  
Current Source ◽  
Second Order ◽  
Cmos Process ◽  
Current Mirror ◽  
First Order ◽  
Temperature Range ◽  
Current Reference

This paper proposes a novel second-order temperature-compensated CMOS current reference which exploits a new self-biased current source for first-order temperature compensation and a resistor-free widlar current mirror for second-order temperature compensation. Moreover, by deriving the temperature coefficient (TC) of the reference current, the temperature compensation condition equations together with a design method of minimizing the thermal drift in a required temperature range are presented. Based on these, the circuit is designed in a standard 0.18 μm CMOS process and achieves a very low TC of only 16.9 ppm/°C in a temperature range between -40°C and 120°C, with 1 μA reference current at 27°C. Besides, the current reference can operate at supply voltage down to 1.3 V, with a good supply regulation of 0.5%/V. At 27°C, its power consumption is 8.93 μW.

scholarly journals Photovoltaic retinal prosthesis restores high-resolution responses to single-pixel stimulation in blind retinas

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Naïg Aurelia Ludmilla Chenais ◽  
Marta Jole Ildelfonsa Airaghi Leccardi ◽  
Diego Ghezzi
Keyword(s):  
High Resolution ◽  
Ganglion Cells ◽  
Artificial Vision ◽  
Wide Field ◽  
Retinal Ganglion ◽  
Retinal Neurons ◽  
Retinal Prostheses ◽  
Retinal Stimulation ◽  
Single Pixel ◽  
Pixel Pitch

AbstractRetinal prostheses hold the promise of restoring vision in totally blind people. However, a decade of clinical trials highlighted quantitative limitations hampering the possibility of reaching this goal. A key challenge in retinal stimulation is to independently activate retinal neurons over a large portion of the subject’s visual field. Reaching such a goal would significantly improve the perception accuracy in retinal implants’ users, along with their spatial cognition, attention, ambient mapping and interaction with the environment. Here we show a wide-field, high-density and high-resolution photovoltaic epiretinal prosthesis for artificial vision (POLYRETINA). The prosthesis embeds 10,498 physically and functionally independent photovoltaic pixels, allowing for wide retinal coverage and high-resolution stimulation. Single-pixel illumination reproducibly induced network-mediated responses from retinal ganglion cells at safe irradiance levels. Furthermore, POLYRETINA allowed response discrimination with a high spatial resolution equivalent to the pixel pitch (120 µm) thanks to the network-mediated stimulation mechanism. This approach could allow mid-peripheral artificial vision in patients with retinitis pigmentosa.

scholarly journals A 0.026 mm2 Time Domain CMOS Temperature Sensor with Simple Current Source

Micromachines ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 899 ◽  
Author(s):  
Sangwoo Park ◽  
Sangjin Byun
Keyword(s):  
Time Domain ◽  
Temperature Sensor ◽  
Feedback Loop ◽  
Supply Voltage ◽  
Current Source ◽  
Cmos Process ◽  
Voltage Sensitivity ◽  
Temperature Dependent ◽  
Digital Conversion ◽  
Pmos Transistor

This paper presents a time domain CMOS temperature sensor with a simple current source. This sensor chip only occupies a small active die area of 0.026 mm2 because it adopts a simple current source consisting of an n-type poly resistor and a PMOS transistor and a simple current controlled oscillator consisting of three current starved inverter delay cells. Although this current source is based on a simple architecture, it has better temperature linearity than the conventional approach that generates a temperature-dependent current through a poly resistor using a feedback loop. This temperature sensor is designed in a 0.18 μm 1P6M CMOS process. In the post-layout simulations, the temperature error was measured within a range from −1.0 to +0.7 °C over the temperature range of 0 to 100 °C after two point calibration was carried out at 20 and 80 °C, respectively. The temperature resolution was set as 0.32 °C and the temperature to digital conversion rate was 50 kHz. The energy efficiency is 1.4 nJ/sample and the supply voltage sensitivity is 0.077 °C/mV at 27 °C while the supply voltage varies from 1.65 to 1.95 V.

A Wideband 9 GHz LC-VCO with Tail Current Source Array in 0.18-μm RF CMOS Process

2013 ◽  
Vol 364 ◽  
pp. 434-438
Author(s):  
Peng Ma ◽  
Xiang Ning Fan
Keyword(s):  
Tuning Range ◽  
Supply Voltage ◽  
Current Source ◽  
Cmos Process ◽  
Rf Cmos ◽  
Frequency Bands ◽  
Tail Current ◽  
Start Up ◽  
Source Array ◽  
Lc Vco

A wideband 9 GHz LC-VCO with tail current source array based on TSMC 0.18-μm RF CMOS process is presented in this paper. After discussing the start-up conditions, the structure of tail current source array is utilized to lower the power consumption in high frequency bands and guarantee start-up at low frequency bands. Furthermore, to extend the frequency range, a 4-bit switched capacitor array is used. Based on our analysis, a NMOS cross-coupled VCO with 4-bit PMOS tail current source array is implemented. Post-simulation results show that the tuning range is from 6.372GHz to 9.154GHz and the phase noise at 1MHz offset is less than-110dBc/Hz in the entire tuning range. The operating current of the VCO core is from 8.24mA to 13.362mA in the entire tuning range under 1.8V supply voltage. And the area of the proposed VCO is 1177.775μm × 577.54μm, with two buffer stages and pads.

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