The oscillators are the devices that generate oscillatory (AC) output from given DC input. There are different kinds of oscillators based on the output waveform they generate. Like
· Sinusoidal oscillators – they generate sinusoidal (sine) wave output
· Square wave oscillators – they generate square (or rectangular) wave output
· Triangular wave oscillators – they generate triangle or sawtooth wave output
· The most widely used oscillators are sine wave oscillators. Such oscillators are used in
· Transmitters – to generate carrier signal for transmission
· Receivers – to generate local carrier signal to extract IF (intermediate frequency) from mixer
· Modulators – to generate carrier for information signal and generate modulated wave
· RADAR and SONAR – to generate signal that will be transmitted and received back
· RF (Radio Frequency) or AF (Audio Frequency) signal generators
Thus we may list out number of such applications where sine wave oscillators are used. In addition I would say the signal communication is impossible without oscillators.
There are different kinds of Sine wave oscillators based on the components used or based on the output frequency that they generate
1. Based on components means if they produce oscillation using resistors (R) and capacitors (C) then they are called RC oscillators and if they use inductor (L) and capacitor (C) then they are termed as LC oscillators
2. Based on output frequency means if they generate frequency in audio range (20 Hz – 20 KHz) then they are Audio Frequency (AF) oscillators. If they generate frequency in low range (100 – 200 KHz) then they are called Low Frequency (LF) oscillators and last, if they generate frequency in high range (in MHz or GHz) then they are termed as High frequency (HF) or Radio Frequency (RF) oscillators.
I am presenting here two such sine-wave oscillators that uses RC components to generate oscillations and they can generate frequency in AF range as well as RF range. The two oscillators are
1. RC phase shift oscillator
2. Wien bridge oscillator
Both are built using op-amp and it is very easy to build them on bread board or on general PCB with few additional components. So let us first gather the required components, instruments and apparatus.
Instruments required:
· CRO or DSO
· Dual power supply (+15 V & -15 V)
Apparatus required:
· Connecting wires
· CRO probes
· Bread board
Components required:
· LM741 IC
· Resistors – 1 K, 47 KΩ (pot), 1.2 KΩ, 10 KΩ, 22 KΩ
· Capacitors – 0.1 µF
Let us first start with RC phase shift oscillator
RC Phase shift oscillator:
RC oscillator is build using an amplifier and a RC network in feedback. For any oscillator the two prime requirements to generate sustained and constant oscillations are
Fore more detail: Sine wave oscillator using LM741
