Pn junction diode by sarmad baloch
I AM SARMAD KHOSA
BSIT (5TH A)
(ISP)
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8. PN Junction Formation
P-Type semiconductor
having excessive holes
N-Type semiconductor
having excessive free
electrons
Junction
Acceptor
atoms
Donor
atoms
9. Charge Distribution
P N
+
+
+
-
-
-
Positive and negative ions are
created when holes and free
electrons cross the junction and
move to the other side this charge is
called “space charge”
Diffusion
current flows
whenever P and
N materials are
joined together
10. The P-N Junction
•When initially joined
electrons from the
n-type migrate into the p-
type – less electron density
there
•When an electron fills a
hole – both the electron
and hole disappear as the
gap in the bond is filled
•This leaves a region with no free charge carriers – the depletion layer – this layer
acts as an insulator
Slide 10
11. Barrier Potential
P N
+
+
+
-
-
-
Charges of opposite polarities establish “Electric
Field” also known as “Barrier Potential”. This
field prevents any further diffusion current
E
Depletion Region
Barrier potential is also
known as “Junction
Potential” or “Diffusion
Potential”. It is denoted by Vo
.
12. Barrier Potential
• Silicon has potential barrier drop of
0.7V.
• Germanium has potential barrier
voltage drop of 0.3V.
14. DIODE
• A PN Junction is also called DIODE.
• Term diode from the Greek roots di , meaning 'two',
and ode, meaning 'path'.
• It is used in various electronics application.
• We will use this diode to form transistor and FET.
• Same diode are also used to form logic circuit
21. To Remember!
•Diode cannot conduct in reverse bias condition.
•Diode can conduct in forward bias condition.
•Silicon diode has voltage drop of 0.7V
•Germanium has voltage drop of 0.3V
