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Lesson Plan on PN-Junction
Topic: PN-Junction Diode
Level: School level (10+2)
Duration: 3 Hours
Teaching Methodology: 1 hr Classroom Session + 1 hr Lab Session (LTspice) + 1 hr problem solving
and assessment.
Relative advantage:
Of Simulation:
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It allows student to change the doping of the semiconductor and see the current flow at
different biasing conditions.
It allows student to vary the biasing conditions and see the current flow at forward and
reverse bias condition.
It allows student to see the change in energy levels of semiconductor as they are doped.
Selection criteria:
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This simulation matches with the content and depth of topic
The simulation matches with the learning goals.
It is very easy to operate and use.
Instructional strategy:
This class is being taken in a lab well-equipped with desktops for strength of 30 students.
Classroom session (1 hr):
Learning Objective(s):
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Student should be able to describe physical operation of PN-Junction.
Student should be able to:
o Predict the net current flow in forward bias and reverse bias situation
o Describe how n and p dopants change energy levels in the semiconductor
These instructional goals will be achieved by showing a PN-Junction diode circuit simulation under
forward and reverse bias condition. Students will be able to change the value of externally applied
potential through -4 Volts to +4 Volts to induce forward and reverse bias situation and can see the
electron flow in the circuit.
(0-10 minutes)
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What instructor does?
o
o
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Instructor first introduces the topic that he is going to teach PN-Junction
diode. He has already taught pre-requisite topics i.e. semiconductor types,
doping etc.
Instructor shows a video on formation and working of PN-Junction diode.
e.g. slides from videos are shown below:
What students do?
o Students watch this video on formation and working of PN-Junction and take
notes.
(10-20 minutes)

What instructor does?
o Instructor administers a questionnaire round on the video.
Sample questions from the questionnaire are:
1) Can we take a slab of P-type semiconductor and physically join it to
another N-type semiconductor to get PN-junction? Yes/ No
2) During forward bias P-type semiconductor is connected to positive
terminal of battery and N-type semiconductor is connected to negative
terminal of battery…. True/False

What students do?
o Students answer the questionnaire.
(20-40 minutes)

What instructor does?
o He lectures on the formation and physical working of PN-junction diode and
addresses students’ clarification questions

What students do?
o Students listens to the lecture and take notes
o They ask clarification questions.
(40-50 minutes)

What instructor does?
o He shows the simulation file to the students already installed in the desktops
and asks them to play and explore with the simulation.
Screenshots of simulation is shown below:
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What students do?
o Students play with the simulation for 10 minutes.
(50-60 minutes)

What instructor does?
o Instructor flashes a questionnaire on the board or projector and asks for
student response.
 E.g. 1) How do you change the doping in the simulation?
2) How do you change the value of bias voltage in the simulation?
3) How do you recognize the change in energy level of
semiconductors?
4) How do you recognize the flow of electrons in forward and
reverse bias situation?

What students do?
o Students respond to the questionnaire by raising their hand.
Lab session (1 hr):
Learning Objective(s):
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Student should be able to simulate I/O (V-I) characteristics of p-n junction diode using LTspice simulation software.
Students are familiar with LT-spice simulation software.

What instructor does?
o Instructor demonstrate students how to plot I-V characteristics of a forward biased
PN-Junction diode and ask them to do the same for reverse bias condition.

What students do?
o Students follow the instructor’s procedure to plot I-V characteristics of forward bias
PN-Junction diode and then they plot I-V characteristics of reverse bias PN-Junction
diode on their own.
Problem solving and assessment (1 hr):

Learning Objective(s):
o Student should be able to apply the concept of forward and reverse biasing and
predict the net current flow
o Student should be able to find the number of electrons and holes generated when
semiconductor materials are mixed with dopants
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What instructor does?
o Instructor will give a set of questions of different difficulty level. It will be a
written assessment and questions are to be solved individually within one
hour.
What students do?
o Students follow the instructor’s instructions and attempts those questions
within one hour
Sample Questions
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The number of silicon atoms per m3 is 5 × 1028. This is doped simultaneously with 5 ×
1022 atoms per m3 of Arsenic and 5 × 1020per m3 atoms of Indium. Calculate the number
of electrons and holes. Given that ni = 1.5 × 1016 m–3. Is the material n-type or p-type?
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Suppose a ‘n’-type wafer is created by doping Si crystal having 5 × 10 atoms/m with 1ppm
concentration of As. On the surface 200 ppm Boron is added to create ‘P’ region in this
wafer. Considering ni = 1.5 × 10 m , (i) Calculate the densities of the charge carriers in the n
& p regions. (ii) Comment which charge carriers would contribute largely for the reverse
saturation current when diode is reverse biased.
28
16
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3
–3
In a p-n junction diode, the current I can be expressed as
𝐼 = 𝐼𝑜 exp (
𝑒𝑉
− 1)
2𝑘𝐵𝑇
where I0 is called the reverse saturation current, V is the voltage across the diode and is positive for
forward bias and negative for reverse bias, and I is the current through the diode, kB is the Boltzmann
constant (8.6×10–5 eV/K) and T is the absolute temperature. If for a given diode I0 = 5 × 10–12 A and T =
300 K, then
(a) What will be the forward current at a forward voltage of 0.6 V?
(b) What will be the increase in the current if the voltage across the diode is increased to 0.7 V?
(c) What is the dynamic resistance?
(d) What will be the current if reverse bias voltage changes from 1 V to 2 V?
Submitted By - Abhinav Anand & Anurag Deep