3
Quad Capacitance
Capacitance of Schottky diode
quads is measured using an
HP4271 LCR meter. This
instrument effectively isolates
individual diode branches from
the others, allowing accurate
capacitance measurement of each
branch or each diode. The
conditions are: 20 mV R.M.S.
voltage at 1 MHz. Agilent defines
this measurement as “CM”, and it
is equivalent to the capacitance of
the diode by itself. The equivalent
diagonal and adjacent capaci-
tances can then be calculated by
the formulas given below.
In a quad, the diagonal capaci-
tance is the capacitance between
points A and B as shown in the
figure below. The diagonal
capacitance is calculated using
the following formula
C
1
x C
2
C
3
x C
4
C
DIAGONAL
= _______ + _______
C
1
+ C
2
C
3
+ C
4
A
C
1
C
C
2
C
4
B
C
3
The equivalent adjacent
capacitance is the capacitance
between points A and C in the
figure below. This capacitance is
calculated using the following
formula
1
C
ADJACENT
= C
1
+ ____________
1 1
1
–– + –– + ––
C
2
C
3
C
4
This information does not apply
to cross-over quad diodes.
Linear Equivalent Circuit Model
Diode Chip
R
j
R
S
SPICE Parameters
Parameter Units
B
V
C
J0
E
G
I
BV
I
S
N
R
S
P
B
P
T
M
V
pF
eV
A
A
Ω
V
HSMS-282x
15
0.7
0.69
1E - 4
2.2E - 8
1.08
6.0
0.65
2
0.5
C
j
R
S
= series resistance (see Table of SPICE parameters)
C
j
= junction capacitance (see Table of SPICE parameters)
R
j
=
8.33 X 10
-5
nT
I
b
+ I
s
where
I
b
= externally applied bias current in amps
I
s
= saturation current (see table of SPICE parameters)
T = temperature,
°K
n = ideality factor (see table of SPICE parameters)
Note:
To effectively model the packaged HSMS-282x product,
please refer to Application Note AN1124.
ESD WARNING:
Handling Precautions Should Be Taken To Avoid Static Discharge.
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
