8/22/2005
Example A Junction Diode Circuit empty.doc
1/3
Jim Stiles
The Univ. of Kansas
Dept. of EECS
Example: A Junction
Diode Circuit
Consider the following circuit with two junction diodes:
The diodes are identical, with n = 1 and I
S
= 10
14
A.
Q:
If the current through the resistor is 6.5 mA, what is the
voltage of source V
S
??
A:
This is a
difficult
problem to solve ! Certainly, we cannot
just write:
=
S
V
and then the answer.
Instead, let’s just determine
what we
can
, and see what happens !
D
i
2
+
−
D
v
2
D
i
1
+
−
D
v
1
+

+
−
R
v
V
S
6.5 mA
100
Ω
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8/22/2005
Example A Junction Diode Circuit empty.doc
2/3
Jim Stiles
The Univ. of Kansas
Dept. of EECS
1)
If 6.5 mA flows through a
0.1 K resistor, the voltage
across that resistor is:
R
v
=
2)
If the voltage across the resistor is 0.65 V, then the
voltage across the diode D
2
, which is
parallel
to the resistor, is
the
same
value:
2
D
v
=
3)
If we know the
voltage
across a pn junction diode, then we
also know its
current
!
−
⎡
⎤
⎡
⎤
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 Spring '09
 Mechatronics, Pn junction, Junction Diode Circuit

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