Upload
xafran-khan
View
217
Download
0
Embed Size (px)
Citation preview
7/29/2019 Electronics 1 2
1/18
7/29/2019 Electronics 1 2
2/18
P-N Junction
When a p-n junction is
formed, some of the free
electrons in the n-region
diffuse across the
junction and combine withholes to form negative
ions. In result they leave
behind positive ions at
the donor sites as shownin the figure below.
7/29/2019 Electronics 1 2
3/18
P-N Junction (Depletion Region)
When a p-n junction
is formed, some of
the electrons from the
n-region which havereached the
conduction bandare
free to diffuse across
the junction andcombine with holes.
http://hyperphysics.phy-astr.gsu.edu/hbase/solids/dsem.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/solids/dsem.html7/29/2019 Electronics 1 2
4/18
P-N Junction (Depletion Region)
Filling a hole makes a negative ion and
leaves behind a positive ion on the n-side.
A space charge builds up, creating a
depletion region which inhibits any further
electron transfer unless it is helped by
putting a forward bias on the junction
7/29/2019 Electronics 1 2
5/18
P-N Junction (Depletion Region)
7/29/2019 Electronics 1 2
6/18
DIODE
A P-N junction device
having two terminals
anode and cathode is
called diode.
7/29/2019 Electronics 1 2
7/18
Diode Characteristics
Forward Biased
If the voltage is applied in such a way that
positive terminal of the battery is connected to
the P-type terminal (Anode) and negative withthe N-type terminal (cathode) of a diode. This
assists electrons in overcoming the space
charge in depletion region. Electrons will flow
with very small resistance in the forwarddirection.
7/29/2019 Electronics 1 2
8/18
Forward Biased
7/29/2019 Electronics 1 2
9/18
Forward Biased
Silicon diodes require 0.7V to assist electrons in
overcoming the space charge in depletion region
7/29/2019 Electronics 1 2
10/18
Forward Biased
7/29/2019 Electronics 1 2
11/18
Reverse Biased:
If the voltage is applied in such a way that
positive terminal of the battery is
connected to the N-type of the diode and
negative with the P-type of a diode then itfurther impedes the flow of electrons
across the junction.
7/29/2019 Electronics 1 2
12/18
Reverse Biased:
Reverse Bias causesto widen the depletionregion
During reverse biaseda very small amountof current flows whichis in pico amperes.This current is calledthe reverse saturationcurrent or leakagecurrent.
7/29/2019 Electronics 1 2
13/18
Diode Characteristic Curve
7/29/2019 Electronics 1 2
14/18
Diode as a Rectifier
The process of converting AC in to DC is
called Rectification. The most common
and widely used application of diode is
rectification.
Half Wave Rectifier
Full Wave Rectifier
Bridge Rectifier
7/29/2019 Electronics 1 2
15/18
Half Wave Rectifier
The simplest kind of rectifier circuit is the
half-wave rectifier.
It only allows one half of an AC waveform
to pass through to the load.
7/29/2019 Electronics 1 2
16/18
Half Wave Rectifier
7/29/2019 Electronics 1 2
17/18
Full Wave Rectifier
To rectify AC power to obtain the full use
ofboth half-cycles of the sine wave, a
circuit consisting of two diodes is used and
is called full wave rectifier.
We use the centre tapped transformer in it
which increases the cost as well as size of
the circuit
7/29/2019 Electronics 1 2
18/18
Full Wave Rectifier