This document analyzes different oscillator circuits using Multisim software. It discusses RC, LC, and crystal oscillators and how feedback is important for stability, impedance, gain, and noise reduction. It then simulates and describes the outputs of a phase shift oscillator using an op-amp, a Colpitts oscillator using BJT, and a Hartley oscillator using BJT. The document observes that oscillators take time to produce steady sinusoidal waves from DC supply and that op-amps produce better stabilized outputs than transistor circuits.

1. Analysis of Different Oscillator
Circuit using Multisim Software
Submitted to Submitted by
Mr.Dr.J.Ajayan Rishi.PL
Faculty of SNS College of Technology Department of ECE
Department of ECE (Student 2018-19)

2. Oscillator
Oscillators are the electronic circuits that generates the periodic
signals often sinusoidal wave or square wave from the input dc (direct
current) supply. The oscillators are used in major electronic application.
The important types of oscillators are
 RC Oscillator
 LC Oscillator
 Crystal Oscillator
The effect of feedback circuits are used in oscillator to
derive the high stability, high input impedance, better stabilized voltage
gain, improved frequency response, lower output impedance and
reduced noise, linear operation but due to feedback voltage gain is
reduced. Due to other major criteria are obtained from feedback the
reduction of voltage gain is not taken as a negative effect. Thus
feedback is important parameter in the oscillator circuit.
The below block diagram represents the oscillator in the
feedback representation
Block diagram of oscillator

3. In this chapter I had covered the three basis amplifier in different
modes of circuit in BJT (bipolar junction transistor), FET (Field
Effect Transistor) and Operational amplifier with basic problems
(problems are derived from book Electronic Devices and Circuit
Theory by Robert L. Boylestad). In below I am listed the oscillator
simulated and covered.
Books Used:
I had used main resources of book Electronic Devices
and Circuit Theory by Robert L. Boyestad.

4. Software used for simulation: Multisim
Online Source used: NPTEL
PHASE SHIFT OSCILLATOR:
Phase shift oscillator circuit produced the oscillation
and phase shift exactly 180 degree. The phase shift oscillator simulation
and problems are discussed below.
Phase shift oscillator using op-amp (Operational Amplifier) in
Multisim simulation:

5. Phase shift oscillator using op-amp (Operational Amplifier) Output:
Problem:

6. For the above circuit the frequency could be calculated for an
oscillator (or) we can determine resistance value for the desired
frequency. Thus the equation and calculation is described below
f = 1/2*pi*RC*root of 6
pi = 3.14, R= 10k, C=0.001 micro farad
f= 153.8 Hz
Therefore the above frequency produced for the circuit is 153 Hz.
Colpitts Oscillator:
The colpitts oscillator designed with the inductance and
capacitance to the transistor feedback network. The below colpitts
oscillator designed using BJT(Bipolar Junction Transisitor).
Colpitts oscillator using BJT (Bipolar Junction Transistor) in
Multisim simulation:

7. Colpitts Oscillator Output:
Problem:
For the above circuit the frequency could be calculated for an
oscillator (or) we can determine resistance value for the desired
frequency. Thus the equation and calculation is described below
f = 1/2*pi*root of L and C
C1=82 pf , C2= 82pf, L=320 micro H
f = 43 Khz
Therefore frequency for the above colpitts oscillator is 43 Kilo Hertz.
Hartley Oscillator:
The Hartely oscillator designed with the inductance and capacitance
to the transistor feedback network. The below colpitts oscillator
designed using BJT(Bipolar Junction Transisitor). The circuit was
invented in 1915 by American engineer Ralph Hartley.

8. Hartely oscillator using BJT (Bipolar Junction Transisitor) in
Multisim simulation:
Hartely Oscillator Output:

9. Observation and Inference:
From this experiment I have been observed that the oscillator doesn’t
produces the signal when starting the demonstration. Thus oscillators are
taking dc supply and starts with some oscillation and start to produce the
exact sinusoidal signal. The observed diagram and its correct statements
are mentioned below.
The build-up of steady state oscillation is illustrated
above figure with envelope covering the initial to steady state sinusoidal
wave of oscillator. Further I had observed that the oscillator produces
better output in operational amplifier than the transistor circuit. Op-
amp(Operational Amplifier) produces better stabilized output that I had
observed during my demonstration. In this report I can’t able to
demonstrate experiment in practical laboratory due to short time period
so, in future I would complete this demonstration with practical in
laboratory condition.
Thus the effect of feedback plays major role in oscillator circuits
whereas thanks for Control Systems and Engineering makes me to
understand the feedback concepts and make me to complete this report
quickly.