Varactor Diode

1
Varactor Diode
REPORT BY
JOHN PAOLO LABARO
2
VARACTOR DIODE
-Also known as Varicap Diode
-Is a device whose reactance can be varied in a
controlled manner with a bias voltage.
-It is a p-n junction with a special impurity
profile, and its capacitance variation is very
sensitive to reverse-biased voltage.
3
Continuation Varactor Diode
-Are widely used in parametric amplification,
harmonic generation, mixing, detection, and
voltage-variable tuning
-It was established that there is a region of
uncovered charge on either side of the junction
that together the regions makes up the
duplication region and define the depletion width
Wd.
4
The transmission capacitance (Ct) established by
the isolated uncovered charges is determined by
A
______
CT ?
Wd
Where ? is the permitivity of the semiconductor
materials, A the p-n junction area and Wd the
depletion width.
5
(No Transcript)
6
The characteristics of a typical commercially
available varicap diode.
C(pF)
C(0)
80 60 40 20 0
-2 -4 -6 -8 -10 -12 -14
VR(V)
(VR applied reverse bias)
7
In terms of the applied reversed bias, the
transition capacitance is given approximately
K
CT
(VT VR)n
Where
K constant determined by the semiconductor
material and construction technique
VT knee potential
VR magnitude of the applied reverse-bias
potential
n ½ for alloy junctions and ½ for diffused
junction
8
In terms of the capacitance at the zero-bias
condition C(0), the capacitance as a function of
VR.
C(0)
CT(VR)
(1 VR/VT)n
9
The symbols most commonly used for the varactor
diode and a first approximation for its
equivalent circuit in the reverse-bias region.
CT f (VR)
Rs
RR ? 1MO
LS
(0.1 - 12O)
(1 5nH)
10
This is an Example of Varactor Diode
11
THANK YOU AND GOD BLESS!!!