PHYSICS – 2024
Semiconductor Electronics
MANU G.A. (9742835053)
On the basis of energy bands distinguish between a conductors (metals),
semiconductor and an insulator.
CONDUCTORS SEMICONDUCTORS INSULATORS
It has low resistivity It has moderate resistivity It has high resistivity
They allow current to pass Their electrical properties They don‟t allow current
through it lies between that of to pass through it
conductors and
insulators
conductivity decreases conductivity increases Their conductivity is zero
with increase in with increase in
temperature temperature
Conductivity is due to free Conductivity is due to No electrons or
electrons both electrons and holes for
holes conductivity.
Conduction band is Conduction band is Conduction band is
completely filled with partially filled with completely empty
electrons at above 0K electrons above 0K
Distinction between Intrinsic and Extrinsic semiconductor
Intrinsic semiconductor Extrinsic semiconductor
1 These are pure semiconductor 1 These are doped semiconductors
2 Conductivity is due both electrons 2 Conductivity is mainly due to
and holes. majority charge carriers.
3 Conductivity is low. 3 Conductivity is high.
4 = 4
5 Conductivity depends on the 5 Conductivity depends on the
temperature. temperature and also doping
level.
,Distinguish between p – type and n – type semiconductors.
p – type semiconductor n – type semiconductor
1 Trivalent dopants are used 1 Pentavalent dopants are used
2 It has acceptor impurity 2 It has donor impurity
3 The majority charge carriers are holes
3 The majority charge carriers are
electrons
4 The minority charge carriers are 4 The minority charge carriers are
electrons holes
5 Acceptor energy level is slightly 5 Donar energy level is slightly below
above the top of the valence band. the bottom of the conduction
band .
6 >>> 6 >>>
Forward biasing of diode : -
The diode is said to be forward biased when p –side is connected to +ve
terminal and n – side is connected to –ve terminal of the battery.
During forward bias
The width of depletion region decreases and
Junction potential decreases
The charge carriers cross the junction and electric current flows through the circuit.
Forward bias offers negligibly small resistance and hence the diode conducts.
Current is due to majority charge carriers.
Reverse biasing of diode : -
The diode is said to be forward biased when p –side is connected to –ve terminal and
n – side is connected to +ve terminal of the battery.
During reverse bias
The width of depletion region increases
Junction potential increases
Reverse bias offers high resistance
Current is due to minority charge carriers.
, 1. Half wave rectifier: -
A device which converts AC to DC is called a rectifier and the process is called
rectification.
It is a device which converts only one half cycle of ac into dc.
During the positive half cycle of input AC voltage i.e. When „A‟ is +ve the diode
is forward biased and it conducts. As a result current flows through the R L and produces
output across it.
During negative half cycle of input A.C voltage i.e. when „A‟ is – ve the diode is
reverse biased so it does not conduct. So we can‟t get the output. The input and output
wave forms of half wave rectifier are as shown in figure.
2. Full wave rectifier: -
A device which converts AC to DC is called a rectifier and the process is called
rectification.
Full wave rectifier is a device which converts both the half cycles of ac into dc.
During the positive half cycle of input AC voltage, A is positive and B is negative the
diode D1 is forward biased so D1 conducts. The diode D2 is in reverse biased and hence
D2 does not conduct. As a result the current I flows through R L and produces output
across the RL.
During the negative half cycle of input AC voltage, A is negative and B is positive the
diode D1 is reverse biased so D1 does not conducts. The diode D2 is in forward biased
and hence D2 conducts. As a result the current I flows through RL and produces output
across the RL.
Semiconductor Electronics
MANU G.A. (9742835053)
On the basis of energy bands distinguish between a conductors (metals),
semiconductor and an insulator.
CONDUCTORS SEMICONDUCTORS INSULATORS
It has low resistivity It has moderate resistivity It has high resistivity
They allow current to pass Their electrical properties They don‟t allow current
through it lies between that of to pass through it
conductors and
insulators
conductivity decreases conductivity increases Their conductivity is zero
with increase in with increase in
temperature temperature
Conductivity is due to free Conductivity is due to No electrons or
electrons both electrons and holes for
holes conductivity.
Conduction band is Conduction band is Conduction band is
completely filled with partially filled with completely empty
electrons at above 0K electrons above 0K
Distinction between Intrinsic and Extrinsic semiconductor
Intrinsic semiconductor Extrinsic semiconductor
1 These are pure semiconductor 1 These are doped semiconductors
2 Conductivity is due both electrons 2 Conductivity is mainly due to
and holes. majority charge carriers.
3 Conductivity is low. 3 Conductivity is high.
4 = 4
5 Conductivity depends on the 5 Conductivity depends on the
temperature. temperature and also doping
level.
,Distinguish between p – type and n – type semiconductors.
p – type semiconductor n – type semiconductor
1 Trivalent dopants are used 1 Pentavalent dopants are used
2 It has acceptor impurity 2 It has donor impurity
3 The majority charge carriers are holes
3 The majority charge carriers are
electrons
4 The minority charge carriers are 4 The minority charge carriers are
electrons holes
5 Acceptor energy level is slightly 5 Donar energy level is slightly below
above the top of the valence band. the bottom of the conduction
band .
6 >>> 6 >>>
Forward biasing of diode : -
The diode is said to be forward biased when p –side is connected to +ve
terminal and n – side is connected to –ve terminal of the battery.
During forward bias
The width of depletion region decreases and
Junction potential decreases
The charge carriers cross the junction and electric current flows through the circuit.
Forward bias offers negligibly small resistance and hence the diode conducts.
Current is due to majority charge carriers.
Reverse biasing of diode : -
The diode is said to be forward biased when p –side is connected to –ve terminal and
n – side is connected to +ve terminal of the battery.
During reverse bias
The width of depletion region increases
Junction potential increases
Reverse bias offers high resistance
Current is due to minority charge carriers.
, 1. Half wave rectifier: -
A device which converts AC to DC is called a rectifier and the process is called
rectification.
It is a device which converts only one half cycle of ac into dc.
During the positive half cycle of input AC voltage i.e. When „A‟ is +ve the diode
is forward biased and it conducts. As a result current flows through the R L and produces
output across it.
During negative half cycle of input A.C voltage i.e. when „A‟ is – ve the diode is
reverse biased so it does not conduct. So we can‟t get the output. The input and output
wave forms of half wave rectifier are as shown in figure.
2. Full wave rectifier: -
A device which converts AC to DC is called a rectifier and the process is called
rectification.
Full wave rectifier is a device which converts both the half cycles of ac into dc.
During the positive half cycle of input AC voltage, A is positive and B is negative the
diode D1 is forward biased so D1 conducts. The diode D2 is in reverse biased and hence
D2 does not conduct. As a result the current I flows through R L and produces output
across the RL.
During the negative half cycle of input AC voltage, A is negative and B is positive the
diode D1 is reverse biased so D1 does not conducts. The diode D2 is in forward biased
and hence D2 conducts. As a result the current I flows through RL and produces output
across the RL.
