Doubt regarding astable multivibrator

[Raj89]

I have designed an op amp type astable multivibrator using TL082 op amp. I need to find out the maximum and minimum frequency of oscillation possible for the circuit at the output. How do i find it? Please explain.
Also, please tell me the values of R and C connected to the non inverting terminal of op amp respectively for maximum and minimum frequency of oscillation.

 

[Grossel]

What kind of oscillator (schematic)

Hi.

First of all I recomend you to visit tinypic.com/ (or any other image hosting site that doesn't require login to view an image), upload the schematic and provide a usable link here.

Alternatively you can find a similar schematic on the web, and then provide a link.

Why I write this (yes, I know you want to ask): Because there is many ways to make an opamp oscillator.

Here is the limitation factors (that I can come up with - there may be more):

• Output characteristic - slope of flanks (can't remember the correct term right now)
• maximum output voltage p^-p^
• What kind of waveform? Sinus, rectangular or triangle?
• Is there any capasitive load at opamp output?

 

[Raj89]

The link for the diagram is : https://circuitscan.homestead.com/files/ancircp/rc_multivibrator.gif
The op amp used is TL082. Please specify the maximum frequency of oscillation, minimum frequency and respective R & C values for the two cases.

 

[BrownOut]

Hi.

First of all I recomend you to visit tinypic.com/ (or any other image hosting site that doesn't require login to view an image), upload the schematic and provide a usable link here.

Or else just attach the schematic directly to your post. Use "Go Advanced" then the paperclip to attach a drawing.

 

[Raj89]

I have attached the entire problem statement for which i need to submit the solution. Please tell the proceedings regarding the frequency,R & C part.

 

[carbonzit]

I have designed an op amp type astable multivibrator using TL082 op amp. I need to find out the maximum and minimum frequency of oscillation possible for the circuit at the output. How do i find it? Please explain.
Also, please tell me the values of R and C connected to the non inverting terminal of op amp respectively for maximum and minimum frequency of oscillation.

Sorry, but your request is ridiculous.

Not because of all your difficulties in posting pictures, which you seem to have resolved.

You're asking us to solve this contest problem for you. Why should we do that?

We could do that ourselves and win the contest, if we cared to. Why should we give away the answer to you?

Do you want something for nothing?

People here are willing to help others with problems. But you need to show us 1) that you have enough electronics knowledge to make use of helpful advice and 2) that you're willing to work out problems on your own, with help from others as needed.

We're not here to give you convenient answers to quiz questions.

 

[BrownOut]

I have designed an op amp type astable multivibrator using TL082 op amp. I need to find out the maximum and minimum frequency of oscillation possible for the circuit at the output. How do i find it? Please explain.
Also, please tell me the values of R and C connected to the non inverting terminal of op amp respectively for maximum and minimum frequency of oscillation.

The equation is given in the attachment. T = 2RC*ln((1+β)/(1-β)). Just solve for T, and you can get the frequency: f=1/T. Simple.

The Max frequency equation is also given. Just use the given equation.

 

[Grossel]

Agreed with carbonzit here that just give a straigt answer wont make thing easier for you.

But I have a question for you. Do you understand HOW this circuit works? I want you to go ahead and tell how YOU think the circuit works. Hint: it partially works as a schmitt trigger.

If you tell first, I would do a little efford to explain if you're stuck.

 

[Raj89]

Sorry but you took it in the wrong sense. I don't want you to solve the problem entirely for me. I just need some guidance. As per the data sheet of Tl802 op amp, two values of slew rate is given, i.e 8(min) and 13(typ). Now which one to use. Anyway it's clear that i need to make the R and C value as low as possible to get the maximum frequency. But i am confused about the maximum limit possible for it. Now, if you could help.

 

[BrownOut]

I would use the "typ" value, then run the simulation and see if it is close. If you're using a TI802 sim model, it probably is usning the typ(typical) value.

 

[Raj89]

I tried with the typ value i.e 13 in Pspice software. But the theoretical frequency which i get as the maximum doesn't match with the simulation result. I mean both the values aren't close at all.

 

[BrownOut]

Let's see your work.

 

[Raj89]

Let's see your work.

Please check the simulation response. Hope you believe me now.

 

[BrownOut]

Who said I didn't believe you? You said your sim didn' match your calculated value. I asked to see your work so I can tell if you made an error.

 

[Raj89]

ok . Please spot the answer and guide me the right way.

 

[Raj89]

I meant spot the error.

 

[carbonzit]

You need to show your work. We need more than just the square-wave output of your simulation.

 

[BrownOut]

I'll need to see your work if I am to spot an error. You've shown almost nothing so far.

 

[Raj89]

Just explain me this : What is the logic behind finding the maximum and minimum frequency of oscillation of an op amp type astable multivibrator ? What is the general approach ?

 

[BrownOut]

Just explain me this : What is the logic behind finding the maximum and minimum frequency of oscillation of an op amp type astable multivibrator ? What is the general approach ?

The answer is here:

https://www.electro-tech-online.com/threads/doubt-regarding-astable-multivibrator.120475/#post991838