Oscillator is a mechanical or electronic device works on the principle of oscillation i.e. a periodic fluctuation between two things based on changes in energy. It is of two types; linear oscillators and non linear oscillators. The wave shape and amplitude are determined by the design of the oscillator circuit and choice of component values.

1. Oscillators

2.  It is an electronic circuit that produces a periodic, oscillating signal often a
square wave and a sine wave.
 Converts direct current from a power supply to an alternating current signal.
 Common signals generated by the oscillators includes clock signals, sound
signals produced by video games, electronic beepers and broadcast signals by
television and radio transmitters.
Introduction

3. Conditions For Oscillations
 The loop phase shift must be 0 ͦand 360 ͦ.
 The loop gain must be slightly greater than unity.
 The voltage gain around the closed feedback loop Acl is the product
of the amplifier gain Av and the attenuation B of the feedback
circuit.
Acl = AvB

4.  A loop gain greater than 1 will rapidly cause the output to saturate at
both peaks of the waveform and producing unacceptable distortion.
 If the amplifier gain is greater than 100, it will cause the oscillator
limit both peaks of the waveform.

5. Oscillator Circuit
Oscillator Circuit is divided into three sections:
Tank
Circuit
Amplifier Circuit
Feedback Circuit

6.  Tank Circuit produces oscillations which are amplified by the transistor
and produces amplified output in the collector side.
 Amplifier circuit basically amplifying the small sinusoidal oscillations
present in the base-emitter circuit and generates output in the amplified
form.
 Feedback circuit fed back the energy of the collector circuit to the base
circuit through the phenomenon of Mutual induction.

7. Types Of Oscillator
Oscillator Types
Linear or Harmonic
Oscillator
Non Linear or
Relaxation oscillator
Feedback
Oscillator
Negative
Resistance
oscillator
LC Oscillator
RC Oscillator
Crystal
Oscillator

8. LC Oscillator
 In LC oscillators, the inductor and capacitor are connected in parallel
form a Tank circuit.
 Tuned circuit can store electrical energy oscillating at its resonant
frequency.
 Used in radio frequency circuits because of their ease of implementation
and good phase noise characteristics.

9. Types of LC Oscillator
LC Oscillator
Hartley Oscillator Colpitts Oscillator Clapps Oscillator
Used to generate high-
frequency waveforms
or signals into which
the oscillation
frequency is
determined by a tank
circuit comprising of
two inductors and
one capacitor.
Used to produce an
oscillation at certain
frequency and it take
feedback from the
active device from the
voltage divider made of
two capacitors in
series across the
inductor.
Constructed from a
transistor and
positive feedback
network using the
combination of an
inductance with a
capacitor for
frequency
determination.

10. RC Oscillator
 Type of feedback oscilIator consist of an amplifying device, resistor, vacuum
tubes and op amps.
 To achieve positive feedback output energy is fed back to its input through a
network of resistors and capacitors.
 RC filter type combinations are preferred to generate sine waves at low
frequencies.

11. Types of RC Oscillator
LC Oscillator
Wien Bridge
Oscillator
Phase shift
oscillator
Used to generate sine
waves at a large range
of frequencies and has
a two stage RC
coupled amplifier
circuit that has low
distortion and good
stability at its resonant
frequency
Linear electronic circuit
that produces a sine
wave output whose
output is fed back to its
input through a phase
shift network consisting
of resistors and
capacitors in a ladder
network.

12. Crystal Oscillator
It is an electronic oscillator used to create an electrical signal of precise
frequency by using the vibrating crystal mechanical resonance made of
piezoelectric material.

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