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Appendix V - Note on transient time
If the capacitance and resistivity component of the measurement apparatus and of the DUM (C
and R
) are different from zero, a constant voltage V
m
transfer to the DUM, but it will instead be governed by the following equation,
,
where V
(t) is the voltage at the DUM at a time t, with R = R
DUM
resistance and capacitance of the measurement apparatus and DUM. RC has the unit of measure of
time and is usually indicated as the time constant τ of the system (τ = RC). If a voltage V
t=0, V
(τ)≈0.63 V
.
DUM
0
Therefore, for each acquired data point Delay must be 9/10 time larger than the time constant RC.
For Ossila FACT1, with two meter-long BNC cable, typical value of resistance and capacitance are R =
1.4 Ω and C = 250 pF, which gives negligible time constant τ.
The time constant τ is sometimes more conveniently expresses in term of the cutting off frequency
f
,
c
.
In addition to the device time constant, the dielectric capacitance charging time and, more
importantly, the transistor ON/OFF frequency. While the former time constant is described by EqA1,
with f
ranging 1250 KHz for SiO
c
.
A2
In Eq A2, μ is the mobility, V
28
Here, we assume that the resistance and capacitance elements of both DUM and measurement apparatus
are in series and parallel, respectively.
Ossila Ltd
to 9 KHz for Al
O
, the latter is given by
2
2
3
the drain voltage and L is the channel length.
DS
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applied at time t=0 will not instantaneously
0
+ R
and C = C
m
DUM
DUM
Eq A1
28
+ C
total
m
DUM
is applied at
0
Eq
100
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