User`s guide

Agilent 4155C/4156C User’s Guide Vol.2, Edition 6 9-7
Built-in Functions
DIFF
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)