02-05-2012, 10:59 AM
A Memristor SPICE Implementation and a New Approach for Magnetic Flux-Controlled Memristor Modeling
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INTRODUCTION
THE three traditional fundamental circuit elements are resistors
®, capacitors ©, and inductors (L). All of them
have two terminals only. These basic devices are based on the
conjunction of the four electrical base units charge q, current
i, voltage v, and magnetic flux φ. With two of these units
combined a total of six combinations is possible theoretically.
Two of them are already defined via time variable t: i = dq/dt
and v = dφ/dt. The three basic circuit elements R, C, and L
can be obtained via derivations of the base units:
SIMULATION PROGRAM FOR INTEGRATED CIRCUITS EMPHASIS (SPICE) IMPLEMENTATION
In [1], an equivalent circuitry for a memristor was proposed
using discrete active circuit elements. Unfortunately, the count
of active devices needed to emulate the memristive effect is so
high that it cannot be applied to simulate circuits with a high
memristor count. Because of this reason it is more appropriate
to describe the memristive behavior. Since a memristor is a
primitive device we created a behavior model of a memristor at
device level using the SPICE circuit description language. This
implementation is not bound to other physical SPICE models or
devices since it applies the use of ideal dependent sources only.
ALTERNATIVE MODEL
The shown SPICE implementation (macro model) for a
charge-controlled memristor model exactly reproduces the results
from [2]. However, these simulation results do not have a
good compliance—not even qualitatively—with the characteristic
form of I/V curves of manufactured devices. Therefore,
(3)–(9) try to approach memristor modeling from a different
point of view to get a closer match to the measured curves
from [2], [6]–[11] even with a simple linear drift of w. Besides
the charge steering mechanism of a memristor modeled in [1]
and [2] also defined a functional relationship for a memristor,
CONCLUSION
In summary, a SPICE implementation for a charge controlled
memristor model is presented based on equations published
in [2]. The implementation is discussed and considers all relevant
aspects for simulation, thus enabling analysis and design
of complex circuits. To get a closer match of simulation results
to measured curves an alternative new model describes
the behavior of a memristor from another viewpoint, which is
applying a mechanism that is controlled by the magnetic flux.
Although microscopic details of the relationship between memductance
and the tunnel current is not finally solved resp. proven
simulation results already show good conformity to published
measurements.