Electronic circuit design ee 233 final presentation

ELECTRONIC CIRCUIT DESIGN EE 233
• FINAL PROJECT PRESENTATION
• BEEE ( SEMESTER-SPRING 2015)
• ABASYN UNIVERSITY
ISLAMABAD
• PRESENTED TO:
THE MOST RESPECTABLE
• SIR WAQAS AHMAD
2

Group Members:
Waseem Abbas Maneri 0379
Faraz Ahmad 0378
Afzaal Hasnain 0334
3

Title:
Hartley and Colpitts Oscillators.
4

HARTLEYAND COLPITTS OSCILLATORS. (FINAL PRESENTATION)
Outline…..
1. Hartley Oscillator
I. Introduction
II. Circuit Diagram
III. Circuit Components and Operation
IV. Tank Circuit
V. Applications
VI. Advantages and Disadvantages
2. Colpitts Oscillator
I. Intro….
II. Circuit and Operation
III. Advantages and Disadvantages
3. References
5

HARTLEYAND COLPITTS OSCILLATORS. (FINALPRESENTATION)
What is Oscillator..?
An oscillator is a mechanical or electronic device that works on
the principles of oscillation.
o Oscillation: A periodic fluctuation b/w two things based
on energy.
Computer, clocks,watches,radios and metal detectors are among
the many devices that uses oscillators.
“OR”
The electronic circuit that produce periodically oscillating
electronic signals such as sine wave, square wave or any other
wave is termed as Oscillator.
6

Hartley Oscillator.
Hartley oscillator was invented in 1915 by the
American engineer Ralph Hartley while he
was working for the Western Electric
company. The original design was tube based
and he got a patent for it in the year 1920.
7

Basic Circuit Diagram:
8

Circuit Components & its
Operation:
In the circuit diagram:
When input is applied
• R1 and R2 give a potential divider bias
for the transistor Q1.
• Re is the emitter resistor, whose job is
to provide thermal stability for the
transistor.
• Ce is the emitter by pass capacitors,
which by-passes the amplified AC
signals.
9

Operation Continue…
• Cin is the input DC decoupling
capacitor while Cout is the output DC
decoupling capacitor.
• The task of a DC decoupling capacitor
is to prevent DC voltages from
reaching the succeeding stage.
• Inductor L1, L2 and capacitor C1 forms
the circuit named as Tank Circuit.
10

Tank Circuit:
Components
I. 2 inductors
II. 1 capacitor
Function:
The function of Tank Circuit is to determine the
oscillation frequency,
11

Operation Continue…
 Supply ON
 Ic Increases
 C1 [Charging & discharging]
 This create oscillation in Tank
circuit.[Key]
 Vout inphase with VL1 & 180o out of
phase with VL2.
 VL2 is fedback to BQ1[Creates another
180 phase shift]
 Total Phase Shift=360o
 An important condition for creating
oscillation.
12

Frequency of the Hartley oscillator.
 Frequency expressed by the given
formula.
 C is the Capacitance [Tank Circuit].
 LT=L1+L2 [Tank Circuit] [different cores]
 L=L1+L2+2M [same core].
 Where M is mutual inductance b/w the
coils.
13

Application:
1) Hartley oscillators are
mainly used in radio
receivers.
2) Particularly uses for good
quality sine wave signal.
3) Useful for the use in RF
range frequency .
4) Due to its wide range of
frequencies it is the most
popular oscillator (30 KHz to 30
MHz).
5) Above this range Colpitts
oscillator is preferred.
14

Advantages & Disadvantages :
Advantages
 The frequency is simply varied by the net value of
C in the tank circuit.
 The output amplitude remains constant when tuned
over the frequency range.
 The feedback ratio of L1 to L2 remains constant.
Disadvantages
 The output is rich in harmonic content and
therefore not suitable where a pure sine wave is
required.
15

Colpitts Oscillator:
The Colpitts Oscillator, (named after its inventor Edwin Colpitts) is
another type of LC oscillator design. In many ways, the
Colpitts oscillator is the exact opposite of the Hartley
Oscillator we have discussed in previous slides. Just
like the Hartley oscillator, the tuned tank circuit
consists of an LC resonance sub-circuit connected
between the collector and the base of a single stage
transistor amplifier producing a sinusoidal output
waveform.
16

Circuit components
& its operation:
 This circuit is very similar in
operation to the Hartley
oscillator
 But the Colpitts LC tank
circuit consists of a single
inductor and two capacitors.
 The values of the two
capacitors (connected in
series) are chosen so their
total capacitance in
series(CTOT), is given by:
17

Operation….
Colpitts Tank Circuit:
 Uses a capacitive voltage divider network as
its feedback source.
 C1 and C2 are placed across a single
common inductor, L as shown.
 Advantage is that (Less mutual inductance=
freq.. Stability is improved)
18

Operation….
 When Supply ON.
 C1 & C2 start (charg…&
discharg…)
 When C1,C2 (fully dischar..)
the E.S energy gets
transferred into the inductor as
magnetic flux.
 Inductor start discharg.. & the
capacitors gets charged again.
 As a result Oscillations are
produced due to the back and
forth transfer of energy b/w
inductors and capacitors.
19

HARTLEY AND COLPITTS OSCILLATORS. (FINAL PRESENTATION)
Continue…
 Vc2 has opposite phase to that of Vc1.
 Vc2 is fedback to the base of transistor which appears in the
amplified form on the output side of transistor [across collector-
emitter].
 Tank ckt produce 180o P.shift and transistor produce another 180o
P.shift.
 As the result Input=Output [inphase]
20

Frequency of Oscillation:
Frequency can be find by the given
formula
 Where L = inductance,
 C = effective capacitance,
 If C1 and C2 are the individual
capacitance, then
C= (C1C2)/(C1+C2).
21

Advantages and Disadvantages:
Advantages:
1. Good wave purity .
2. Fine performer at high frequency .
3. Good stability at high frequency .
4. Wide operation range 1 to 60 MHz .
Disadvantages:
1. Poor isolation (Load impedance vs.. frequency) .
2. Hard to design .
22

HARTLEY AND COLPITTS OSCILLATORS. (FINALPRESENTATION)
References:
 www.electronics-tutorials.ws › Oscillator
 www.learnabout-electronics.org/Oscillators/osc21.php
 www.learnabout-electronics.org/Oscillators/osc21.php
 https://www.elprocus.com/colpitts-oscillator
 www.circuitstoday.com/colpitts-oscillator
23

24

25

Electronic circuit design ee 233 final presentation

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Electronic circuit design ee 233 final presentation

Similar to Electronic circuit design ee 233 final presentation (20)

Recently uploaded

Recently uploaded (20)

Electronic circuit design ee 233 final presentation