Hello, friends welcome to another interesting post. In this post, we will discuss the Operating Principles of Oscillator. The oscillator such configuration provides output in the form of a periodic signal after getting dc voltage at the input. There is no need for repetitive signals at the input but only for synchronization for oscillations in certain applications.
The shape or voltage at the output terminal is either a sine wave or non-sine wave according to the type of oscillator used. The 2 main categories of oscillators are feedback oscillator and relaxation oscillator. In this post, we will have a detailed look at oscillator working, operation circuit, and some other related parameters. So let’s get started with Describe Operating Principles of Oscillator.
Describe Operating Principles of Oscillator
- In general, the oscillator transforms the electrical signal provided by the dc source in the periodic signal. The basic circuit configuration of this oscillator is shown below.
Feedback Oscillator
- The category of the oscillator is the feedback oscillator that sends a small value of output signal at the input terminal without any change in phase shift which causes the occurrence of an output signal.
- When oscillaton gets started the loop gain is sustained at the value of on to continue the oscillations.
- The feedback oscillator comprises of the amplifier for gain and positive feedback circuitry which generates phase shift and deliver attenuation process can be seen in the below figure.
Relaxation Oscillators
- The 2nd category of the oscillator is the relaxation oscillator. There is no feedback circuit in this oscillator but it uses an RC timing circuitry to produce a signal which is commonly a square wave signal or non-sinusoidal signal.
- Generally, the relaxation oscillator uses a Schmitt trigger or other components which vary state to for charging and discharging of the capacitor with the use of resistance.
Feedback Oscillators Principle
- The feedback oscillator working principle relies on the operation of positive feedback. This category of the oscillator is normally used to produce a sine waveform.
What is Positive Feedback
- The positive feedback is described by the situation where the part of the output voltage of an amplifier is feedback to the input without the existence of phase shift which causes the occurrence of the signal at the output.
- The general circuit of positive feedback is described here.
- We can see that the in-phase feedback voltage is getting amplification to generate the output voltage that in results generates in the feedback signal.
- Which is a loop is generated which comprises the signal and regular sinewave output that is generated.
- This process is known as oscillation. In certain categories of amplifiers, the feedback circuitry changes the phase, and inverting amplifier is needed to offer another phase shift therefore there is no existence of phase shift.
- It can be seen in figure denoted as b.
Conditions Required for Oscillation
- The 2 conditions required for oscillation explained in the below figure.
- The phase shift about the feedback loop should be at zero degrees.
- The value of voltage gain is Acl about the closed feedback loop should have value one.
- The voltage gain about the closed feedback loop is Acl is the multiple of amplifier gan and the amplifier gain and the attenuation of circuitry is given here.
Acl = AvB
- If the output required is sinewave the loop gain larger than the one will result in the output to become saturation at both extremes of waveform generating undesired distortion.
- To remove this some category of gain control should be used to retain the loop gain at the exact one when oscillations initiated.
- For instance, if the attenuation of feedback circuitry has a value of 0.01 the amplifier should have again close to one hundred to control the attenuation process and not produce the undesired distortion.
- The amplifier gain of larger than the one hundred will result in the oscillator to restrict both extremes of the signal.
What is Start-Up Conditions
- Till now we have discussed that it oscillator generates a regular or continuous sine waveform output.
- Let us discuss the needs for the oscillation to initiate when the dc source voltage is on.
- As we know that unity gain situations should be needed for oscillation to retained.
- For oscillation to start the voltage gain about the positive feedback loop should be larger than one therefore the amplitude of output can be set to the required point.
- The value of gain should be reduced to one therefore the output retains at the required point and oscillation is retained.
- Both situations for starting and sustaining oscillation are described here.
That is all about the Operating Principles of Oscillator I have mentioned here each point with the details. Thank you for reading
