Agilent Technologies 4156b, User Manual, Page: 347 / 414

Agilent 4155B/4156B User’s Guide Vol.2, Edition 5 7-15
Data Variable and Analysis Function
Built-in Function
DIFF
Returns differential coefficient of 1st expression by 2nd expression .
Syntax
DIFF(
1st expression
,
2nd expression
)
The differential coefficient is defined as follows:
y’
n
= (y
2
- y
1
)/(x
2
- x
1
)
when n = 1
y’
n
= (y
n+1
- y
n - 1
)/(x
n+1
- x
n - 1
)
when 1 < n < N
y’
n
= (y
N
- y
N - 1
)/(x
N
- x
N - 1
)
when n = N
Where,
y’
n
: differential coefficient for measurement index number n.
y
n
: value of 1st expression for measurement index number n.
x
n
: value of 2nd expression for measurement index number n.
N: number of sweep steps or number of samples.
For each primary sweep, use same definition as for basic sweep measurement and
assume measurement index number 1 for the first step of each primary sweep.
Example To return the 2nd order differential coefficient of
ID
by
VG
:
DIFF(DIFF(ID,VG),VG)