RC Phase Shift Oscillator (using Op-Amp) Explained
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- เผยแพร่เมื่อ 17 ส.ค. 2018
- In this video, the RC phase shift oscillator has been explained and the expression of the frequency for this RC phase shift oscillator has been derived.
By watching this video, you will learn the following topics:
0:29 How RC Phase Shift Oscillator Works
1:45 Simple RC Circuit (Phase Lead Circuit)
5:35 Design of RC Shift Oscillator using Op-amp
7:31 Derivation of the frequency for the RC Phase Shift Oscillator
RC Phase Shift Oscillator:
In this oscillator, the RC network is used in the feedback to generate the stable sine wave. This oscillator is the harmonic oscillator (As it generates the sine wave)
RC Phase shift oscillator is used for low-frequency generation (Up to few Hundred of kHz). Typically it is used for the audio frequencies.
In RC Phase Shift Oscillator, the transistor or op-amp in inverting mode is used for the amplification. So, it provides the 180 degrees of phase shift. And the remaining 180 degrees of phase shift is provided by the RC feedback network.
By tuning the gain of the RC network and the amplifier it is possible to achieve the unity loop gain.
In the feedback loop, more than two RC stages are cascaded to achieve the stable phase shift.
If three stages are used for then the attenuation provided by the feedback circuit β= 1/29.
And the frequency of the oscillation f = 1/(2πRC√6)
In general of N stages of the RC circuit are cascaded then
f =1/(2πRC√2N)
In the RC phase shift oscillator, usually the R is kept fixed and C is changed to tune the oscillator. And for proper tuning, all capacitors are ganged together.
This video will be helpful to all the students of science and engineering in understanding the RC Phase Shift Oscillator.
#RCPhaseShiftOscillator
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Besten Dank für dieses Video
Many thanks for this video
from Switzerland
Took me a day because there was no equation number given but it was helpful!!! Thank you
Your derivation was so much better, my lecturer Laplace transformed the circuit and ended up getting 3x3 matrix and the derivation was worth over 5 pages
The timestamps for the different topics covered in the video:
0:29 How RC Phase Shift Oscillator Works
1:45 Simple RC Circuit (Phase Lead Circuit)
5:35 Design of RC Shift Oscillator using Op-amp
7:31 Derivation of the frequency for the RC Phase Shift Oscillator
Good explanation and approach to the results.
thanks a lot, taught me more about circuit analysis!
Loved it👍
Thank you so much
Thank you for detailed explanation sir
Very good video. You have made a good video which can be referred for technical exams.
sir I love the way you explain the topics. please make a video on phase locked loop.
I'm here to just say "Thanks" for sharing awesome knowledge in this 17 minute video.
Thank u so much for this.
Thank you. Very helpful.
Thank you so much for such video! May the Lord Jesus bless you.
Thanks a lot.great explanation
Excelente vídeo, tudo parece tão fácil. Saudações do Brasil
The math is kind of long but i simulated the circuit using LTspice and plotted the ratio of Vout/Vin and it came out to -1/29th as in the video. Thank you. You are so good with the math you should go back for your doctorate.
Did you simulate the rc network and it vout/vin or including the opamp?
Great that you know to use spice
Please educate me a bit about that when you have time
@@abhijithanilkumar4959 do it yourself lazy man.
What is spice
@@deitybasumatary7497 A kind of biryani
your intro is best sir,,,we feel chilled whenever we open any video.....
thanks for this type of kindness😊😊
Man, you are my hero
super ur videos with clean nd good information nd explanantion🤗🤗
It is great .THANK YOU.
It helped me a lot sir
Thnqq 4 the video...it's really helpful
Awesome!
Really nice video :)
kudos from india
Super sir easy to understand... thank you
absolutely love your derivations
Great job
Very helpful👌
excellent explanation sir
thank u
The only reason to recharge my phone is to watch NESO academy and ALL ABOUT ELECTRONICS.
AOE is the real khalnayak
@@abhijithanilkumar4959 What AOE?
@@rishabhpathak1367 All About Electronics
sajan re jhooth mat bolo khuda ke paas jana hai
very cool, you nerd..
Very good explanation
بارك الله فيك وهداك
Great stuff! You always have clear explanations
How about some videos on:
In rush current, FETs, LVDS, Voltage doubler, buck, boost, buck-boost, and flybacks?
Very nice explaination sir 👍👍👍👏👍👏👏
Please upload a video on RC phase oscillator using BJT
Yes please do
Thanks sir🔥
Hi, all about electronics. I just see one error on the diagram: R1 is virtually connected in parallel to R, affecting the gain calculation. Instead, R is in feedback to the input without R1.
THANK so much you Sir .
शानदार explanation... Hartley oscillator भी krao
watching before attempting my 4th try in the exam!
Great! Note - you say "into" when you mean "times"
thank you so much
@9:45 why we are not applying KCL at Vo? in this case it is open but what about when we connect it in the feedback path?
very good
Why is it assumed that the entire current I3 flows through R and is not split into 2 currents, one flowing through the resistor and one flowing out to the right of the circuit? When the RC circuit is connected to the amplifier circuit then there will be a current flowing in at Vin and a current flowing out at Vout, so why is only the current flowing in at Vin applied during the derivation?
Also thought about that
Thank you sir
This may be a stupid question, but if you change R and C in the RC ladder do you change the gain from 1/29 to another value?
Its exactly awesome
Sir the equivalent ckt you draw the output is first taken from opam directly and in second ckt output is taken after the phase shift ckt .will it produce the same output.
Is there a short way or a formula for calculating the attenuation factor(beta)? It will be pretty time consuming to solve such big equations during examinations.
Very good
Here,
Phase shift per attenuator is 60.
so, tan(60)=sqrt(3)=Xc/R
==> Xc=sqrt(3)*R
So, Vin/Vo=1-j*sqrt(3)
And we also know angular frequency , w=1/(j(Vin/Vo-1)*RC)
So, in this case angular frequency , w=1/(sqrt(3)*RC) Not your mentioned : w=1/(sqrt(6)*RC)
Note: I can be wrong, but I found this from my calculation. thanks at all for great video.
What software do you use for this presentation? thanks
i loved it
Super sir...
Hello, can we use voltage divider method?
It would be nice if you provide in the end of you each video a simulation, ex in proteus, of your circuit. So we do know what is really going on. My onpinion.
Thankyou...
Great sir
Thanks
Super sir
Hi, I need to design a rc phase shift oscillator for 150hz can you please help me selecting the values..
many many thanks to ALL ABOUT CIRCUIT for express the RC-phase shift oscilator easy and nice way
Please tell me what program you used to make tutorial. Please tell me sir, thank you. I have screen recorder but I don't know what program for this writing and all
What will be the amplitude of the output sine wave??.....calculation can be made easy by using transfer functions but this is the easiest way to understand....thank you
I think this depends on the op-amp, since this is an oscillator you would have to check the slew rate for the maximum frequency and the rail voltages for the sine wave amplitude.
thanks sir
Hi, how this circuit is in positive feed back? as per my understanding oscillator must be in positive feed back? but this circuit seems to be in negative feed back?
Try to understand in terms of the loop gain of the circuit. For oscillation, AB should be slightly more than 1 right. And around the loop, the phase shift should be either 0 or multiple of 2*pi.
Here the RC feedback circuit attenuates the output signal by the factor 1/29 at the oscillation frequency. And it also introduces the 180 degrees of phase shift between the output of the op-amp and the feedback signal which is again given as input.
On the other end, the op-amp provides the gain of slightly more than 29 and as it is connected in the inverting configuration, it also introduces the 180 degrees of phase shift.
So, overall loop gain becomes slightly more than 1 and the phase shift around the circuit becomes zero.
In short, it satisfies the conditions required for the sustained oscillations.
I hope it will clear your doubt.
Connecting to the negative (inverting) terminal doesn't necessarily signifies that the OPAMP is in negative feedback. Notice that the gain of feedback loop is -1/29, which is itself negative. Hence negative feedback with negative gain (attenuation in this case) cancels each other and the overall feedback is positive.
You are الأفضل يلا... استمر يلا... يا هندي...
Thankyou sir
your videos were useful . Can you give the equations and pictures as a note or text in the description ? thank you
Why using 0 - tan inverse eqn for the phase shift?
I don't understand op amp holds up to 18(VCC) and 18(-VCC)
We need A= 29 ' any help
Gain is ratio between output and input voltage, not the value of output voltage. Let say you input is 0.1V and your output is 2.9V, so 2.9/0.1 = 29 (Gain)
How charging and discharging of capacitors occur through the resistor. can u please explain
Ive watched all your videos for Opamp and you are just amazing ,
here I got a small doubt in 1:19 time of this video you said vout is in 180 phase shift but our input and feedback both are at + i.e non inverting then how come our vout is inverted ?
What I mean to say is, the feedback circuit ( RC Circuit) provides 180 degree phase shift to the incoming signal (output of the opamp) at particular frequency. Therefore at the oscillation frequency, ideally the output of the opamp ( which is input to the feedback circuit) and feedback signal ( output of the RC network) will be 180 degree phase shifted.
Of course, the overall phase shift of the circuit is 360 degree, and that's what we required for oscillation.
I hope it will clear your doubt.
Hi all about electronics. I have just a minor question on 6:34. I am just confused because here the op amp has a negative feedback. Isn't negative feedback used when we want our op amp to function as amplifier and positive feedback if we want to use it as oscillator?
Since this is an RC Phase Shift Oscillator, shouldn't we use positive feedback in it?
Sir, why can’t we use cascaded low pass filters instead of high pass filters?
Sir why 60 deg each nw equally ,is possible to three diff cimbination to achieve 180?
The circuit diagram shown at 5:37 has Vout at terminal of Rf,while redrawn circuit diagram have Vout at terminal of R1 !.How can it be correct? Please clarify my doubt...
thanks in advance.
Yes. It's by mistake. It has to be on the left side.
Anyway thanks for pointing it out.
Would you make a video about op- amps used to perform analog multiplication??
I have made a video on a log and antilog amplifier using the op-amp. In that video, I have explained how the analog multiplication can be performed using the anti-log and log amplifiers.
You can check that video.
Here is the link:
th-cam.com/video/Nrfb-s0wl6g/w-d-xo.html
Just great...thanks
13:16 what's the formula for voltage drop across capacitor?
sir, here feedback is also connected to -ve terminal.. why it is so???
Can anyone tell me how the formula for phase shift came at 2:36
at the ending, you called Vo/Vin the attenuation, I though it was the gain and attenuation was the inverse?
Rushal Bhai..!!Will you please make a video about bootstrapping technique in emitter follower amplifier????
Yes, When I make a videos on transistors, I will cover it.
Could anyone explain how to calculate beta? I thought that as the gain of a single high pass filter with phase 60 was 1/2, that beta would be (1/2)^3. But apparently not
same doubt bro!
@ALL ABOUT ELECTRONICS
hello Sir, from beta=1/29 how we can say gain is >=29, (how greater than is introduced, why not less than)?
what will be the final output voltage level (Vout) ?
what about 4th order RC circuit, is gain is -1/29 or not??
Isnt there a minus is absent in equation of Xc? Zc = jXc = 1/jwC = -j/wC -> Xc= -1/wC ? I am very confused because of it I could not drive the same formulas with you
Why we only change the value of capacitor to get a desired frequency ¬ change the resistor value
Hello , have you samthing about open and closed loop gain?
Sir ,there is a resistance in parallel with capacitance in high pass filter!!
so in this cas, depending on how much RC curcit is cascaded to each other the formula of "f" will change. and since f changed the attenation factor won't be equal to 1/29. right? so we will have to change the gain of opamp. right?
Not only the gain, but you also need the look at the phase. You also need phase of 180 degree, so that the overall phase is 360 degree.
Hello Sir... Can you please make video on wein oscillator using bjt and fet circuit... It would be great help
14:24 , can you elaborate on why the output voltage will have real part only , and can we cascade it with low pass filter and if we can , will there be any change in the result?
In oscillator, although in the input (the thermal noise) there are many frequencies, eventually we are getting the output oscillation only at the specific frequency. So, we can say that there is a sort of resonance at the specific frequency. And in resonance, the input and output are in phase. Therefore, the imaginary part will be zero.
@allaboutelectronics As you mentioned the oscillators have positive feedback then why positive feedback is not employed in this circuit?
Actually there is a positive feedback . The op-amp provides 180 degree phase shift (since it is inverting op-amp). And the RC feedback circuit provides remaining 180 degree phase shift. So, the input which is fed to the op-amp is in phase with the initial seed signal. (noise is the seed signal). I hope it will clear your doubt. If you still have any doubt then let me know here.
How i can find Rf of this oscillator
Good