Department Of Preparatory Cycles
2024-2025
2nd Year
Date 24/01/2025
Duration : 1h / Teacher : Nabila Nouar
Q7 : The effect of forward bias on the depletion
region of a PN junction is that it makes it : ( 0.5 pts )
Test correction • Wider
• More narrow
Electronics
Q8 : Reverse bias of a junction is the condition that (
0.25 pts )
QCM : Choose the correct answer(s) • Allows current in the PN junction
• Prevents current in the PN junction
Q1 : Bohr Model is more accurate than Quantum
model for the Atomic structure description ( 1 pts)
Q9: The following figure refers to the equivalent
• Yes circuit of : ( 0.25 pts )
• No
Q2 : The maximum number of electrons in the third
shell of an atom contains : ( 1 pts )
• 16 electrons
• 18 electrons
• 6 electrons
• 1 electron
Q3 : Ionization refers to : ( 1 pts ) • An ideal
diode in forward region
• Loss of electrons
• An ideal diode in reverse region
• Gain of electrons
• A practical diode in reverse region
• Both
• A complete diode in reverse region
• None
• A complete diode in forward region
Q4 : Conductors have : ( 0.5 pts )
• More electrons in the valence band than Q10 : What is the correct order of elements in a DC
insulators do power supply : ( 0.25 pts )
• Less electrons in the valence band than
• Transformer/rectifier/filter/regulator
insulators do
• Transformer/regulator/filter/rectifier
• Transformer/filter/rectifier/regulator
Q5: Conduction and valence bands are overlapped in • None
: ( 0.5 pts )
• Conductors Q11 : The transformer has a turns ratio that equals to
• Semiconductors ( 0.25 pts )
• insulators 𝑁𝑝𝑟𝑖 𝑉 𝐼
• 𝑁𝑠𝑒𝑐
= 𝑉𝑠𝑒𝑐 = 𝐼𝑠𝑒𝑐
𝑝𝑟𝑖 𝑝𝑟𝑖
Q6 : Adding impurities to modify conductivity of a 𝑁𝑠𝑒𝑐 𝑉𝑠𝑒𝑐 𝐼𝑠𝑒𝑐
material is : ( 0.5 pts ) • = =
𝑁𝑝𝑟𝑖 𝑉𝑝𝑟𝑖 𝐼𝑝𝑟𝑖
𝑁𝑠𝑒𝑐 𝑉𝑠𝑒𝑐 𝐼𝑝𝑟𝑖
• Ionization • 𝑁𝑝𝑟𝑖
=𝑉 =𝐼
𝑝𝑟𝑖 𝑠𝑒𝑐
• Doping • 𝑁𝑜𝑛𝑒
Q12 : which of these are isolation transformers
( 0.25 pts + 0.25 pts):
• 1:2
• 1:1
• 2:1
• 2:2
• 1:3
Q13 : An AND logic gate that is build up with diodes
has an output of ‘1’ ( 0.25 pts )
• If one diode is conducting at least. We have : Eth = 6Ri ; so the Mesh is :
• If all diodes are conducting
6𝑅𝑖 = (𝑒 − 𝑒0 ) − 3𝑅𝑖.
e-RI0
Q14 : An OR logic gate that is build up with diodes So : i = then
9R
will display in the output ‘0’ if ( 0.25 pts )
2
Eth = 3 (𝑒 − RI0 ) (0.5 pts)
• If one diode is blocked at least
• If all diodes are blocked
Exercise 1 : (7 pts)
(0.5 pts)
Eth
I= (0.5 pts)
R th + R 0
Thevenin :
2 𝑒 − RI0
I= (1pts)
3 2R + R0
Norton :
R th = R AB = 3R//6R = 2R (1.5 pts)
R th = R N = 2R (0.5 pts)
2
Department Of Preparatory Cycles
2024-2025
2nd Year
The Mesh gives :
3ηR+R𝐼0 = 𝑒 , which leads to
:
e-RI0
𝜂= (0.5 pts) -Vbias+0.7 = -3.5+0.7=-2.8V (0.25 pts)
3R
• Germanium made diode
Same plot (0.25 pts) but
-Vbias+0.3 = -3.5+0.3=-3.2 V (0.25 pts)
(0.5 pts)
Q2. We consider the following circuit :
RN
𝐼=R 𝜂 ( 0.5 pts)
N +R0
2R e-RI0
= *
2R + R 0 3R
2 e-RI0
I= (1 pts)
3 2R + R 0
1. The name and purpose of the circuit : Center
tapped full wave rectifier (2 pts)
2. ( 0.5 pts + 0.5 pts)
Exercise 2 : (6 pts)
Q1.
1. This circuit is a negative limiter (2 pts)
2. Plot the output voltage if we consider that
the diode is practical and that 𝑉𝐵𝑖𝑎𝑠 = 3.5𝑉
for
• Silicon made diode (0.25 pts)
