EDC NOTES UNIT 1

1. ELECTRONIC DEVICES ANDELECTRONIC DEVICES AND
CIRCUITSCIRCUITS
Faculty:Faculty:
1.Shaik.Jakeer Hussain1.Shaik.Jakeer Hussain
2.P.Sandeep patil2.P.Sandeep patil
3.P.Ramesh Babu3.P.Ramesh Babu

2. UNIT-IUNIT-I
ELECTRON DYNAMICS AND CROELECTRON DYNAMICS AND CRO::
Motion of charged particles in electricMotion of charged particles in electric
and magnetic fields. Simple problemsand magnetic fields. Simple problems
involving electric and magnetic fieldsinvolving electric and magnetic fields
only. Electrostatic and magneticonly. Electrostatic and magnetic
focusing. Principles of CRT,focusing. Principles of CRT,
deflection sensitivity (Electrostaticdeflection sensitivity (Electrostatic
and magnetic deflection), paralleland magnetic deflection), parallel
and perpendicular electric andand perpendicular electric and
magnetic fieldsmagnetic fields

3. Deflection of Electrons in aDeflection of Electrons in a
Uniform Electric FieldUniform Electric Field
Consider an electron beam directedConsider an electron beam directed
between two oppositely charged parallelbetween two oppositely charged parallel
plates as shown below.plates as shown below.
With a constant potential differenceWith a constant potential difference
between the two deflecting plates, thebetween the two deflecting plates, the
trace is curved towards the positivetrace is curved towards the positive
plate.plate.
+
-
d

4. Deflection of Electrons in a UniformDeflection of Electrons in a Uniform
Electric FieldElectric Field
The force acting on each electron inThe force acting on each electron in
the field is given bythe field is given by
d
eV
eEF P
==
where E = electric field strength,
V = p.d. between plates,
d = plate spacing.
p

5. Deflection of Electrons in a UniformDeflection of Electrons in a Uniform
Electric FieldElectric Field
The vertical displacement y is givenThe vertical displacement y is given
byby
22
)(
2
1
2
1
t
md
eV
aty
p
==
2
2
)(
2
1
v
x
md
eVp
=
This is the equation for a parabola.

6. Deflection of Electrons in aDeflection of Electrons in a
Uniform Magnetic FieldUniform Magnetic Field
The force F acting on an electron in aThe force F acting on an electron in a
uniform magnetic field is given byuniform magnetic field is given by
BevF =
Since the magnetic force F is at right angles to
the velocity direction, the electron moves round
a circular path.

7. Deflection of Electrons in aDeflection of Electrons in a
Uniform Magnetic FieldUniform Magnetic Field
The centripetal acceleration of theThe centripetal acceleration of the
electrons iselectrons is
m
Bev
a =
Hence
m
Bev
r
v
a ==
2
which gives
eB
mv
r =

8. Cathode Ray OscilloscopeCathode Ray Oscilloscope
(CRO)(CRO)
The structure of the cathode rayThe structure of the cathode ray
tubetube

9. Cathode Ray OscilloscopeCathode Ray Oscilloscope
ControlsControls
Y-GainY-Gain
Time BaseTime Base

10. Y-GainY-Gain
amplifies the Y-deflectionamplifies the Y-deflection
small input voltages are amplifiedsmall input voltages are amplified
by built-in amplifiers beforeby built-in amplifiers before
applying to the Y-plates.applying to the Y-plates.
Y- Gain = 0.5 V/divY- Gain = 0.5 V/div
– 0.5 volt will cause a vertical deflection0.5 volt will cause a vertical deflection
of 1 divisionof 1 division

11. Time BaseTime Base
is ais a saw-toothsaw-tooth voltage appliedvoltage applied
internally across the X-plates.internally across the X-plates.
time
volts

12. Time BaseTime Base
controls the speed at which thecontrols the speed at which the
spot sweeps across the screenspot sweeps across the screen
horizontally from left to right.horizontally from left to right.
Time taken
for spot to
move across
the screen and
back
Fly backvolts
time0
spot at centre
of screen
spot on left side
of screen
spot on right side
of screen

13. volts
time0
Screen
spot on left side
of screen
spot at centre
of screen
spot on right side
of screen
Fly back

14. Time BaseTime Base
it helps to display the actualit helps to display the actual
waveform of any a.c. appliedwaveform of any a.c. applied
across the Y-platesacross the Y-plates
normally calibrated innormally calibrated in
– s/cms/cm
– ms/cmms/cm
µµs/cms/cm
gives the time required for the spot togives the time required for the spot to
sweep 1 cm horizontally across thesweep 1 cm horizontally across the
screen.screen.

15. Time Base: How It WorksTime Base: How It Works
Time taken for spot to move
across the screen and back
time
volts Fly back
0
spot at centre
of screen
spot on left side
of screen
spot on right side
of screen
A
B
C

16. Uses of c.r.o.Uses of c.r.o.
Measure potential differenceMeasure potential difference
– d.c.d.c.
– a.c.a.c.
Display waveforms of alternating p.d.Display waveforms of alternating p.d.
Measure short intervals of time, andMeasure short intervals of time, and
Compare frequenciesCompare frequencies

17. Measuring d.c. PotentialMeasuring d.c. Potential
DifferenceDifference
switch off the time-baseswitch off the time-base
a spot will be seen on the c.r.o.a spot will be seen on the c.r.o.
screenscreen
d.c. to be measured is applied tod.c. to be measured is applied to
the Y-platesthe Y-plates
spot will either deflected upwardsspot will either deflected upwards
or downwardsor downwards
deflection of the spot isdeflection of the spot is
proportional to the d.c. voltageproportional to the d.c. voltage
appliedapplied

18. Measuring d.c. PotentialMeasuring d.c. Potential
DifferenceDifference
Y-input
y
If the Y-gain control is set
at 2 volts/division
And the vertical
deflection, y, is 1.5
Then d.c. voltage
= 1.5 x 2
= 3.0 V

19. Measuring a.c. voltageMeasuring a.c. voltage
switch off the time-baseswitch off the time-base
a spot will be seen on the c.r.o. screena spot will be seen on the c.r.o. screen
a.c. to be measured is applied to the Y-a.c. to be measured is applied to the Y-
platesplates
spot will move up and down along thespot will move up and down along the
vertical axis at the same frequency as thevertical axis at the same frequency as the
alternating voltagealternating voltage
– spot moves to the top when the voltagespot moves to the top when the voltage
increases to its maximum (positive)increases to its maximum (positive)
– spot moves to the bottom when the voltagespot moves to the bottom when the voltage
decreases to its lowest (negative)decreases to its lowest (negative)

20. Measuring a.c. voltageMeasuring a.c. voltage
When the frequency is highWhen the frequency is high
– the spot will move so fast that a verticalthe spot will move so fast that a vertical
line is seen on the screenline is seen on the screen
Length of the vertical line gives theLength of the vertical line gives the
peak-to-peak voltage (Vpeak-to-peak voltage (Vpppp) applied to) applied to
the Y-platethe Y-plate
The peak voltage (VThe peak voltage (Vpp) is) is
== VVpppp/2/2

21. Measuring a.c. voltageMeasuring a.c. voltage
Y-input
Vpp

22. Measuring a.c. voltageMeasuring a.c. voltage
Vpp
Vp
Vp = Vpp/2

23. C.R.O. as a VoltmeterC.R.O. as a Voltmeter
it has nearly infinite resistanceit has nearly infinite resistance
(between the X- and Y-plates),(between the X- and Y-plates),
therefore draws very little current;therefore draws very little current;
it can be used to measure both d.c.it can be used to measure both d.c.
and a.c. voltages; andand a.c. voltages; and
it has an immediate response.it has an immediate response.

24. Displaying WaveformsDisplaying Waveforms
Set the time-base to a suitableSet the time-base to a suitable
frequency,frequency,
Apply the input to the Y-plateApply the input to the Y-plate
– a steady waveform of the input will bea steady waveform of the input will be
displayed on the c.r.o.displayed on the c.r.o.

25. Displaying WaveformsDisplaying Waveforms
Y-input

26. Displaying WaveformsDisplaying Waveforms
When input voltage frequency is theWhen input voltage frequency is the
samesame as the time-base frequencyas the time-base frequency
Input Voltage
c.r.o. screen

27. Displaying WaveformsDisplaying Waveforms
When input voltage frequency is theWhen input voltage frequency is the
twicetwice the time-base frequencythe time-base frequency
Input Voltage
c.r.o. screen

28. Measuring Short Time IntervalsMeasuring Short Time Intervals
Set time-base to its lowest frequencySet time-base to its lowest frequency
rangerange
Connect microphone to the Y-inputConnect microphone to the Y-input
Blow two short whistles into theBlow two short whistles into the
microphonemicrophone
– two short pulses, at short interval aparttwo short pulses, at short interval apart
will be displayed on the c.r.o. screenwill be displayed on the c.r.o. screen

29. Measuring Short Time IntervalsMeasuring Short Time Intervals
t divisions
If the time-base is 10 ms/division
and
if the separation between pulses
is t divisions
then
time interval is 10t ms
c.r.o. screen

30. Measuring Short Time IntervalsMeasuring Short Time Intervals
Y-input

31. Lissajous’ FiguresLissajous’ Figures
Lissajous’ figure can be displayed byLissajous’ figure can be displayed by
applying two a.c. signalsapplying two a.c. signals
simultaneously to the X-plates andsimultaneously to the X-plates and
Y-plates of an oscilloscope.Y-plates of an oscilloscope.
As the frequency, amplitude andAs the frequency, amplitude and
phase difference are altered,phase difference are altered,
different patterns are seen on thedifferent patterns are seen on the
screen of the CRO.screen of the CRO.

32. Lissajous’ FiguresLissajous’ Figures
Same amplitude but different frequencies