RC phase shift oscillator is a sinusoidal oscillator used to produce sustained well shaped sine wave oscillations. It is used for different applications such as local oscillator for synchronous receivers, musical instruments, study purposes etc. The main part of an RC phase shift oscillator is an op amp inverting amplifier with its output fed back into its input using a regenerative feedback RC filter network, hence the name RC phase shift oscillator.
- Rc Phase Shift Oscillator Pdf
- Rc Phase Shift Oscillator Working Pdf
- Phase Shift Audio Oscillator
- Phase Shift Oscillator Circuit
- Rc Phase Shift Oscillator Experiment Pdf
By varying the capacitor,the frequency of oscillations can be varied. The feedback RC network has a phase shift of 60 degrees each, hence total phase shift provided by the three RC network is 180 degrees. The op amp is connected as inverting amplifier hence the total phase shift around the loop will be 360 degrees. This condition is essential for sustained oscillations. We have already discussed about RC phase shift oscillator using transistor.
An example of an oscillator circuit that follows the basic development of a feedback circuit is the phase-shift oscillator. This circuit is as shown in Figure. Recall that the requirements for oscillation are that the loop gain, Av, is greater than unity and that the phase shift around the feedback network is 180 (providing positive feedback).
Circuit Diagram
Components Required
- Resistors (1.2KΩ, 1KΩx2)
- Potentiometer (50KΩ)
- Capacitors (0.01µFx3)
- 741 Op Amp
Output Waveform beginning
Sustained Output Waveform
Working of RC Phase shift oscillator
- The feedback network offers 180 degrees phase shift at the oscillation frequency and the op amp is configured as an Inverting amplifier, it also provide 180 degrees phase shift. Hence to total phase shift around the loop is 360=0degrees, it is essential for sustained oscillations.
- At the oscillation frequency each of the resistor capacitor filter produces a phase shift of 60° so the whole filter circuit produces a phase shift of 180°.
- The energy storage capacity of capacitor in this circuit produces a noise voltage which is similar to a small sine wave, it is then amplified using op amp inverting amplifier.
- By taking feedback, the output sine wave also attenuates 1/29 times while passing through the RC network, so the gain of inverting amplifier should be 29 in order to keep loop gain as unity.
- The unity loop gain and 360 degree phase shift are essential for the sustained oscillation.
- RC Oscillators are stable and provide a well shaped sine wave output with the frequency being proportional to 1/RC and therefore, a wider frequency range is possible when using a variable capacitor.
- However, RC Oscillators are restricted to frequency applications because at high frequency the reactance offered by the capacitor is very low so it acts as a short circuit.
Why it uses 3 RC stages?
- Number of RC stages help improve the frequency stability. The total phase shift introduced by the feedback network is 180 degrees, if we are using N RC stages each RC section provide 180/N degree phase shift.
- When 2 RC sections are cascaded, the frequency stability is low. For 3 sections cascaded the phase change rate is high so there is improved frequency stability. However for 4 RC sections there is an good phase change rate resulting in the most stable oscillator configuration. But 4 RC sections increases cost and makes circuit complexity.
- Hence phase shift oscillators make use of 3 RC sections in which each section provides a phase shift of 60 degree. The latter is generally used in high precision applications where cost is not much regarded and only accuracy plays a major role.
Design
Frequency of oscillation (F):
Gain of the Op Amp inverting amplifier (G):
Attenuation offered by the feedback RC network is 1/29, so the gain of inverting amplifier should be 29
Use Ri=1.2 KΩ
So, Rf=35KΩ
Use 50KΩ potentiometer and adjust its value to obtain output on CRO
Components Pin out
i-St@r Lab
Simulated output using Multisim
The oscillators are electronic circuits makes a respective electronic signal generally the sine wave and the square wave. It is very important in other types of the electronic equipment such as quartz which used as a quartz oscillator. The amplitude modulation radio transmitters use the oscillation to generate the carrier waveform. The AM radio receiver uses the special oscillator it is called as a resonator to tune a station. The oscillators are present in the computers, metal detectors and also in the guns. The different types of oscillators are explained below.
What is Meant by Oscillator?
The oscillator works on the principle of the oscillation and it is a mechanical or electronic device. The periodic variation between the two things is based on the changes in the energy. The oscillations are used in the watches, radios, metal detectors and in many other devices use the oscillators.
Principle of Oscillators
The oscillator converts the direct current from the power supply to an alternating current and they are used in many of the electronic devices. The signals used in the oscillators are a sine wave and the square wave. The some of the examples are the signals are broadcasted by the radio and television transmitter, clocks which are used in the computers and in the video games.
Types of Oscillators
There are two types of electronic oscillator’s they are linear and nonlinear oscillators. The linear oscillators give the sinusoidal input. The linear oscillators consist a mass m and its force in the linear in equilibrium. By applying the hook’s low the spring creates the force that i9s in linear for small displacements.
The different types of oscillators are mentioned below and some of them are explained.
- Armstrong Oscillator
- Crystal Oscillator
- Hartley oscillator
- Colpitts Oscillators
- Cross-Coupled Oscillator
- Dynatron Oscillator
- Meissner Oscillator
- Optoelectronic Oscillator
- Phase Shift Oscillator
- Wine Bridge Oscillator
- Robinson Oscillator
- Tri-Tet Oscillator
Armstrong Oscillator
The Armstrong oscillator is an LC electronic oscillator and to generate this oscillator we are using the inductor and the capacitor. In 912 the US engineer Edwin Armstrong has invented the Armstrong oscillator and it was the first oscillator circuit and also in 1913 this oscillator was used in the first vacuum tube by the Alexander Meissner who as an Austrian engineer.
The Armstrong oscillator is known as the tickler oscillator because of the individual features of the feedback signal should produce the oscillations are magnetically coupled to the tank indicator. Let us consider the coupling is weak, but the sustain oscillation is sufficient. The following equation shows the oscillation frequency f. The Armstrong oscillator is also called as the Meissner oscillator or tickler oscillator.
Rc Phase Shift Oscillator Pdf
f = 1 / 2Π√LC
To achieve the 180-degree phase shift oscillation, the Armstrong oscillation uses the transistor, which is shown in the above figure. From the figure, we can observe that the output is from the primary transformer it has a transistor and the feedback is taken from the secondary coil of the transformer. By seeing the polarity dots in the transformer secondary coil is inverted using the primary coil. The operating frequency is obtained by the capacitor C1 and the primary of the transformer.
Hartley Oscillator
Rc Phase Shift Oscillator Working Pdf
The Hartley oscillator is an electronic oscillator. The frequency of this oscillation is determined by the tuned circuit. The tuned circuit consists of the capacitor and inductor, hence it is an LC oscillator. In 1915 by American engineer Ralph Hartley has invented this oscillator. The features of the Hartley circuit are the tuned circuit consists of a single capacitor in parallel with the two inductors which are in series. From the center connection of the two inductors for oscillation purpose, the feedback signal is taken. Follow the below link to know more about Hartley Oscillator Circuit and Its Working
The Hartley oscillator is parallel to the Colpitts apart from that it uses a pair of tapping coils as an alternate of two tapped capacitors. From the below circuit the output voltage is developed across the inductor L1 and the feedback voltages are across the inductor L2. The feedback network is given in the mathematical expression which is given below
Feedback network = XL2 / XL1 = L 2 / L 1
Applications
Phase Shift Audio Oscillator
- This oscillation will produce a desired range of frequencies
- The Hartley oscillators are used in the radio frequency in a range of the 30Mhz
- In radio receiver, this oscillator is used and it has a wide range of frequency
Colpitts Oscillator
The Colpitts Oscillator was by American engineering by Edwin H. Colpitts in the year of 1918. This oscillator is a combination of both inductors and capacitor. The features of the Colpitts Oscillator are the feedback for the active devices and they are taken from the voltage divider and made up of two capacitors which are in series across the inductor. Follow the below link to know more about Collpits Oscillator Working and Its Applications
The Colpitts circuits consist of gain devices such as the bipolar junction, field effect transistor, operational amplifier and vacuum tubes. The output is connected to an input in a feedback loop it has a parallel tuned circuit and it functioned as a band-pass filter is used as a frequency of the oscillator. This oscillator is an electrically dual of the Hartley oscillator hence the feedback signal is taken from the inductive voltage divider it has two coils in the series.
The following circuit diagram shows the common base Colpitts circuit. The inductor L and the both the capacitors C1 & C2 are in series with the parallel resonant tank circuit and it gives the frequency of the oscillator. The voltage across the C2 terminal is applied to the base-emitter junction of the transistor to create the feedback oscillations.
Applications
Phase Shift Oscillator Circuit
- It is used to generate the sinusoidal output signals with a very high frequency
- Very wide range of frequencies is involved
- It is used in the radio and mobile communications
- In commercial purpose, many applications are used
Multi-Wave Oscillator
The multi-wave oscillator was invented by the French engineer by Georges Lakhovsky in the year of 1920 to 1940. He showed that the nucleus of the cell with the filaments stands, it is very similar to the electronic oscillator and it has the capability of receiving & sending the vibratory information. The multi-wave oscillators are experimental, research for the historical instrument, and there is a no medical claim is made. The multi-wave oscillator unit presents the printed circuit board Golden ratio antenna.
Applications
- The healing action of this oscillation is very bad because of the holistically work
- The healing process is done by all parts of the body
- The MWO is used in many countries worldwide by individual
- This oscillator is applied for the treatment of the cancer
This article describes the different kinds of oscillator circuits and its application. I hope by reading this article you have known about the different types of oscillators and its application. If you have any queries regarding this article or to implement any electronics projects please, feel to comment in the below section. Here is a question for you, what type oscillator does not have the LC oscillators?
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