152 research outputs found
Application of Maxwell-Wagner polarisation in monolithic technologies
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A Biomimetic Model of the Outer Plexiform Layer by Incorporating Memristive Devices
In this paper we present a biorealistic model for the first part of the early vision processing by incorporating memristive nanodevices. The architecture of the proposed network is based on the organisation and functioning of the outer plexiform layer (OPL) in the vertebrate retina. We demonstrate that memristive devices are indeed a valuable building block for neuromorphic architectures, as their highly non-linear and adaptive response could be exploited for establishing ultra-dense networks with similar dynamics to their biological counterparts. We particularly show that hexagonal memristive grids can be employed for faithfully emulating the smoothing-effect occurring at the OPL for enhancing the dynamic range of the system. In addition, we employ a memristor-based thresholding scheme for detecting the edges of grayscale images, while the proposed system is also evaluated for its adaptation and fault tolerance capacity against different light or noise conditions as well as distinct device yields
Computing shortest paths in 2D and 3D memristive networks
Global optimisation problems in networks often require shortest path length
computations to determine the most efficient route. The simplest and most
common problem with a shortest path solution is perhaps that of a traditional
labyrinth or maze with a single entrance and exit. Many techniques and
algorithms have been derived to solve mazes, which often tend to be
computationally demanding, especially as the size of maze and number of paths
increase. In addition, they are not suitable for performing multiple shortest
path computations in mazes with multiple entrance and exit points. Mazes have
been proposed to be solved using memristive networks and in this paper we
extend the idea to show how networks of memristive elements can be utilised to
solve multiple shortest paths in a single network. We also show simulations
using memristive circuit elements that demonstrate shortest path computations
in both 2D and 3D networks, which could have potential applications in various
fields
An RRAM biasing parameter optimizer
Research on memory devices is a highly active field, and many new technologies are being constantly developed. However, characterizing them and understanding how to bias for optimal performance are becoming an increasingly tight bottleneck. Here, we propose a novel technique for extracting biasing parameters, conducive to desirable switching behavior in a highly automated manner, thereby shortening the process development cycles. The principle of operation is based on: 1) applying variable amplitude, pulse-mode stimulation on a test device in order to induce switching multiple times; 2) collecting the data on how pulsing parameters affect the device’s resistive state; and 3) choosing the most suitable biasing parameters for the application at hand. The utility of the proposed technique is validated on TiOx-based prototypes, where we demonstrate the successful extraction of biasing parameters that allow the operation of our devices both as multistate and binary resistive switches
Emulating long-term synaptic dynamics with memristive devices
The potential of memristive devices is often seeing in implementing
neuromorphic architectures for achieving brain-like computation. However, the
designing procedures do not allow for extended manipulation of the material,
unlike CMOS technology, the properties of the memristive material should be
harnessed in the context of such computation, under the view that biological
synapses are memristors. Here we demonstrate that single solid-state TiO2
memristors can exhibit associative plasticity phenomena observed in biological
cortical synapses, and are captured by a phenomenological plasticity model
called triplet rule. This rule comprises of a spike-timing dependent plasticity
regime and a classical hebbian associative regime, and is compatible with a
large amount of electrophysiology data. Via a set of experiments with our
artificial, memristive, synapses we show that, contrary to conventional uses of
solid-state memory, the co-existence of field- and thermally-driven switching
mechanisms that could render bipolar and/or unipolar programming modes is a
salient feature for capturing long-term potentiation and depression synaptic
dynamics. We further demonstrate that the non-linear accumulating nature of
memristors promotes long-term potentiating or depressing memory transitions
An Adiabatic Capacitive Artificial Neuron With RRAM-Based Threshold Detection for Energy-Efficient Neuromorphic Computing
In the quest for low power, bio-inspired computation both memristive and
memcapacitive-based Artificial Neural Networks (ANN) have been the subjects of
increasing focus for hardware implementation of neuromorphic computing. One
step further, regenerative capacitive neural networks, which call for the use
of adiabatic computing, offer a tantalising route towards even lower energy
consumption, especially when combined with `memimpedace' elements. Here, we
present an artificial neuron featuring adiabatic synapse capacitors to produce
membrane potentials for the somas of neurons; the latter implemented via
dynamic latched comparators augmented with Resistive Random-Access Memory
(RRAM) devices. Our initial 4-bit adiabatic capacitive neuron proof-of-concept
example shows 90% synaptic energy saving. At 4 synapses/soma we already witness
an overall 35% energy reduction. Furthermore, the impact of process and
temperature on the 4-bit adiabatic synapse shows a maximum energy variation of
30% at 100 degree Celsius across the corners without any functionality loss.
Finally, the efficacy of our adiabatic approach to ANN is tested for 512 & 1024
synapse/neuron for worst and best case synapse loading conditions and variable
equalising capacitance's quantifying the expected trade-off between
equalisation capacitance and range of optimal power-clock frequencies vs.
loading (i.e. the percentage of active synapses).Comment: This work has been accepted to the IEEE TCAS-
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