CH
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Vishay Sfernice
Revision: 08-Feb-18
5
Document Number: 53014
For technical questions, contact: sferthinfilm@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
The complex impedance of the chip resistor is given by the following equations:
Notes
• = 2 x x f
• f: Frequency
The chip resistor itself is purely resistive when . The smaller the L x C product the greater the frequency range over
which the resistor looks approximately resistive.
This can be seen on the graphs showing the ratio versus frequency.
R, L and C are relevant to the chip resistor itself.
L
c
and C
g
also depends on the way the chip resistor is mounted.
It is important to notice that after assembly the external reactance of L
c
and C
g
will be combined to internal reactance of L and
C. This combination can upgrade or downgrade the HF behavior of the component.
This is why we are displaying two sets of data:
• versus frequency curves which aims to show at a glance the intrinsic HF performance of a given chip resistor
• S-parameters versus frequency curves relevant to chip resistor when assembled on ideal Z0 impedance transmission line
These lines are terminated with adapted source and load impedance respectively Z
s
and Z
l
with Z
0
= Z
L
= Z
s
(for others
configurations please consult us).
Equivalent circuit for S-parameters:
S-parameters are computed taking into account all the resistive, inductive and capacitive elements (Z total) and Z
0
= Z
L
= Z
s
= R.
Z
R j L R
2
C – L
2
C
2
–+
1CR
2
C 2L–
2
L
2
C
4
++
--------------------------------------------------------------------------------------
=
Z
R
--------
1
1 CR
2
C 2L–
2
L
2
C
4
++
------------------------------------------------------------------------------------------
x 1
L R
2
C – L
2
C
2
–
R
------------------------------------------------------------
2
+=
tan
1– L R
2
C – L
2
C
2
–
R
------------------------------------------------------------
=
L
c
C
g
Z
0
C
L
R
Z total
Z
0
L
c
Z
S
G
Z
L
C
g
