Electronic Oscillator ,classification ,linear and non linear ,circuit description , tank circuit ,working and operation , frequency of oscllation and Applications

1. Electronic
oscillator
 The electronic
circuit that produces
periodically oscillating
electronic signal such
as sine wave, square
wave or any other
wave is termed as
Electronic Oscillator.

2. Classicification
 Oscillators can be
classified into different
types generally based on
their output frequency.
 Electronic oscillators can
be termed as voltage
controlled oscillators as
their frequency of
oscillations can be
controlled by their input
voltage.
 Foremost electronic
voltage controlled
oscillators can be
considered as two types
namely: Linear Oscillator
and Nonlinear Oscillator.

3. Non linear oscillator

4. Linear
oscillators Linear oscillators are
used to produce
sinusoidal output
waveforms and are
further classified into
many types, such as
Feed back oscillator,
Negative resistance
oscillator, Colpitts
oscillator, Hartley
oscillator, Armstrong
oscillator, Phase shift
oscillator, Clapp oscillator,
Delay line oscillator,
Pierce oscillator, Wien

5. Colpits osillator

6. INVENTION
Colpitts oscillator were
invented and designed by
an American Engineer
EDWIN H.COLPITTS in
1916.

7. 1)The Colpitt’s oscillator is designed for
generation of high frequency sinusoidal
oscillations (radio frequencies ranging
from 10KHz to 100MHz).
2)They are widely used in commercial
signal generators up to
100MHz………………
3)Colpits oscillator is same as Hartely
oscillator except for one
differnce,instead of using a tapped
inductance colpits oscillator uses a

9. Circuit Discription
 It consist of an R-C coupled amplifier using
an n-p-n transistor in CE configuration. R1
and R2 are two resistors which form a
voltage divider bias to the transistor. A
resistor RE is connected in the circuit which
stabilizes the circuit against temperature
variations. A capacitor CE is connected in
parallel with RE, acts as a bypass capacitor
and provides a low reactive path to the
amplified ac signal.
 The coupling capacitor CC blocks dc and
provides an ac path from the collector to the
tank circuit.

10. FEEDBACK
NETWORK OR TANK
CIRCUIT
 The feedback network (tank circuit)
consists of two capacitors C1 and C2
(in series) which placed across a
common inductor L.
 The centre of the two capacitors is
tapped (grounded).
 The feedback network (C1, C2 and L)
determines the frequency of oscillation
of the oscillator..

11. Working and
operation When the collector supply voltage Vcc is
switched on, collector current starts
rising and charges the capacitors C1 and
C2.
 When these capacitors are fully
charged, they discharge through coil L
setting up damped harmonic oscillations
in the tank circuit.
 The oscillatory current in the tank circuit
produces an a.c. voltages across C1,
C2.
 The oscillations across C2 are applied
to base-emitter junction of the transistor

12. Frequency of oscillation
 The frequency of these oscillation can
be determined by using resonant
frequency of tank circuit consisting of
inductor and capacitors….
 The tank circuit is considered as
energy reservior or energy storage…

13.  The feedback voltage ( across the
capacitor C2) is 180° out of phase with the
output voltage ( across the capacitor
C1), as the centre of the two capacitors is
grounded.
 A phase shift of 180° is produced by the
feedback network and a further phase shift
of 180° between the output and input
voltage is produced by the CE transistor.
 Hence, the total phase shift is 360° or 0°,
which is essential for sustained

14. Resonant frequancy and
Equivalent capacitence.
 The resonant frequency is given by
ƒr=1/(2П√(L1*C))
 Where ƒr is the resonant frequency
 C is the equivalent capacitance of
series combination of C1 and C2 of
the tank circuit
 It is given as
 C=(C1*C2)/((C1+C2))
 L1 represents the self inductance of
the coil.

15. Applications
 It is used for generation of sinusoidal
output signals with very high
frequencies.
 It is frequently used for the applications
in which very wide range of frequencies
are involved.
 Used for applications in which undamped
and continuous oscillations are desired
for functioning
 It is used for the development of mobile
and radio communications.
 It has many applications used for the
commercial purposes.