Hey friends, welcome to the Kohiki ALL ABOUT ELECTRONICS. In this article, we will talk about the electronic oscillator and we will learn about the basic working principle of the oscillator. the electronic oscillators are used in a wide range of applications.
They are used in laptop and smartphone processors for generating clock signals. While they are used in radio and mobile receivers for generating the local carrier frequency. and even they are used in the signal generators which are used in the lab to test the circuits.
Quick info About
|oscillator||A generator could be a circuit that produces never-ending, repeated, alternating undulation with no input. Oscillator essentially convert one-way current be due to a DC supply into Associate in Nursing alternating undulation that is of the required frequency, as set by its circuit parts|
|what is oscillator||An oscillator is a technical analysis tool that constructs high and low bands between two extreme values, and then builds a trend indicator that fluctuates within these bounds. Traders use the trend indicator to discover short-term overbought or oversold conditions.|
|oscillator hartley||The Hartley Oscillator design uses two inductive coils in series with a parallel capacitor to form its resonance tank circuit producing sinusoidal oscillations|
|oscillator crystal||A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a constant frequency.|
what is oscillator
So, this oscillator accepts the DC voltage and generates the periodic AC signal of the desired frequency. Now, the oscillators can generate frequencies from a few Hz to even GHz. Now, the output of the oscillator can be either a sinusoidal signal or non-sinusoidal signals like a square wave and the triangular wave.
How does OScillator work?
In simple terms, this oscillator circuit is nothing but the amplifier which is given positive feedback. So, let’s understand the working principle of this oscillator. So, let’s say some input sinusoidal signal is applied to this amplifier. So, at the output, the input signal will get multiplied by the gain of this amplifier. And the output signal will be equal to A times the input signal.
Now, let’s say, this output signal is given as an input to this feedback circuit. Now, usually, the feedback circuit used to be a frequency selective circuit of the resonant circuit. And let’s say the output of this feedback circuit is equal to Vf. So, Vf can be written as a β times output voltage. That is equal to Aβ times the input voltage. where here this β is nothing but the feedback fraction. And it defines what fraction of the output voltage is given as feedback to the input stage.
Now, if the phase shift that is introduced by this amplifier and the feedback circuit is zero, in that case, this feedback signal will be in phase with the input signal. Now, let’s say, this feedback signal is getting added to the input signal and at the same time, the input signal is removed from the circuit. So, now this feedback signal Vf will act as an input for this amplifier. So, after removing the input voltage whether we will get the sustained oscillations or not, that depends on the product of this Aand β. And it is known as the loop gain of the oscillator.
so, if this loop gain Aβ is less than 1, in that case over the period of time, the input signal will die out. So, now let’s say in one particular circuit Aβ is equal to 0.9. And in this circuit, the input voltage Vin is equal to 2V of a sine wave. So, now whenever this input signal passes through this amplifier and the feedback circuit, then the input signal Vin will become 2V, multiplied by 0.9.
That is equal to 1.8V. And once again whenever this input signal passes through this loop, then the input signal will get reduced by the factor of 0.9. So, in this way, every time this input signal passes through this loop, the amplitude of the input signal will reduce. And over the period of time, the oscillations in the circuit will die out.
Similarly, whenever this Aβ is greater than1, at that time, the oscillations in the circuit will build up. So, as you can see, in both cases, we are not getting sustained oscillations. And that is only possible whenever this Aβis equal to 1. So, when Aβ is equal to 1, at that time the feedback signal Vf will be the same as the input signal, provided the input signal and the feedback signal have the same phase. So, in that case, we will get the sustained oscillations at the output.
Barkhausen Criteria for Oscillations and mathematical derivation
So, in oscillator to get the sustained oscillations, two conditions should get satisfied. The first is, the product of this Aβ should be equal to 1. And the second is the phase shift of this loop gain should be equal to zero, meaning that whenever the input signal travels through this amplifier and the feedback circuit, the overall phase shift that is introduced by the circuit should be equal to zero. And these two criteria are known as Barkhausen’s criteria for oscillations.
Now, so far we have assumed that whenever the is switched ON, at that time some finite amount of starting voltage is applied to this. But actually, if you see, no signal is applied to this oscillator. And still, we are getting the oscillations at the output. So, the question is how is it possible? How we can get the oscillations at the output without giving any input to this.
So, the answer is, the thermal noise present in every circuit. And if you are aware, this thermal noise contains all frequency components. Starting from a few Hz to even hundreds of GHz. So, initially, whenever this is turned on, all the frequency components of this thermal noise will get amplified by the amplifier. And the amplified output of this thermal noise will be given as an input to this feedback circuit.
Now, as I said earlier, this feedback circuit is the frequency selective circuit. So, out of all the frequency components only for one particular frequency, the phase shift that is introduced by this amplifier and the feedback circuit will be equal to zero. While all other frequencies will have a different phase.
so, from all other frequencies, only one particular frequency will get added with the input noise. And in this circuit, initially, the loop gain Aβ is slightly set more than 1. And because of that the noise signal of a particular frequency will get build up over a period of time. And once this signal reaches a certain voltage at that time, the loop gain of the circuit will become 1. And it is possible because of the non-linear behavior of either amplifier or the feedback circuit.
So, in this way, the noise signal of the desired frequency will get build up over a period of time. And once this signal reaches finite voltage then the loop gain of the circuit will become 1. And in this way, it is possible to get the sustained oscillations at the output. So, this is the basic working principle of the. Now, earlier we had seen the two criteria for the sustained oscillations. And these two criteria can also be proved mathematically.
So, let’s say, the output of the feedback circuit is equal to Vf. And this signal Vf will get added with the input signal. So, suppose if the input signal is present at that time, the input to the amplifier will be equal to Vin +Vf. And at the output, we will get A times (Vin+Vf) Now, where Vf is nothing but β times output voltage.
So, if we put the value of Vf, then Vout will be equal to A times Vin, plus Aβ times Vout. And if we simplify it then we can say that vout/Vin is equal to A/ (1- Aβ) Now, here in the , we are not providing any sort of input signal. And still, we are getting the oscillations. It means that Aβ in the circuit should be equal to 1. So, that this condition will get fulfilled.
So, from this, we can say that the magnitude of this loop gain should be equal to 1 and the phase shift that is introduced by this loop gain should be equal to 0. So, in this way, mathematically these two criteria can also be proved. Now, as I said before, in the feedback circuit used to be a frequency selective circuit.
So, this feedback circuit can be made up of either RL, RC, or RLC components. And even the quartz crystal can be used for the frequency selection.
Different Types of Oscillators
- oscillator hartley
- oscillator crystal
- crystal oscillator
So, depending on the type of feedback circuit, the oscillator can be classified as either RC, LC, or crystal oscillator. And moreover that depending on the arrangement of these components, these can be classified further. Now, the oscillators which are mentioned here are the sinusoidal oscillators. Or even it is known as the harmonic oscillators.
Because the output of these oscillators used to be a sine wave. While some others also provides a different kind of shape. Like square wave and the triangular wave. And these are known as relaxation. And these types of relaxation can be build up either using op-amp or the timer ICs like 555 timers. And we will see the design of the different types in future articles. so, I hope in this article you understood the basic working principle of the oscillator.
What is an oscillator used for?
Oscillators convert direct current (DC) from a power supply to an alternating current (AC) signal. They are widely used in many electronic devices ranging from simplest clock generators to digital instruments (like calculators) and complex computers and peripherals etc.
Which oscillator is more stable?
Quartz Crystal Oscillator
Which oscillator is used for high frequency?
The LC Oscillator is therefore a “Sinusoidal Oscillator” or a “Harmonic Oscillator” as it is more commonly called. LC oscillators can generate high frequency sine waves for use in radio frequency (RF) type applications with the transistor amplifier being of a Bipolar Transistor or FET.
What is the principle of oscillator?
There are many types of electronic oscillators, but they all operate according to the same basic principle: an oscillator always employs a sensitive amplifier whose output is fed back to the input in phase. Thus, the signal regenerates and sustains itself. This is known as positive feedback.
so here are a you tube video based on osci which was uploaded by Afrotechmods
So, if you have any questions or suggestions, do let me know in the comment section below. If you like this article, hit the like button and subscribe to the channel for more such articles.