Characterization of laser thermal loading on
because the internal composition of the device is irrele-
vant. Indeed, not only can memristors be made from differ-
ent materials, they have even been found in amoeba, squids
and plants, and numerous other living beings [5].
Once a device is identified from experimental
measurements to be a memristor, it is natural to develop
a mathematical model which can mimic approximately the
measured pinched hysteresis loops.
For pedagogical reasons, it is convenient to classify
a memristor according to the complexity of its mathemati-
cal representation into the 4 classes listed in Tab. 1, in the
order of decreasing complexity.
The Venn diagram in Fig. 3 shows the memristor
universe and the relationship among the 4 classes of mem-
ristors listed in Tab. 1.
The simplest class of memristors defined in the lowest
part of Tab. 1 is called an ideal memristor, which coincides
with the original definition postulated in [2]. Indeed, we
can recover its constitutive relation, within an arbitrary
constant (0),via
0 (0) ( ) ( ) ˆ q
R d qq q . (1)
Observe that differentiating both sides of (1) with
respect to time t gives
d d R
dt t q d
q (2)
or
v Rq i (3)
upon identifying d
v
dt
and dq
dt i , respectively.
Equation (1), which is equivalent to (2), is called the
constitutive relation of a charge-controlled memristor in
[2], [6], [7]. The dual constitutive relation of a flux-con-
trolled memristor
q q ˆ (4)
is equivalent to the voltage-controlled memristor
i G( ) v , (5)