ok what i mean is, after a few seconds in the simulation it begins oscillating from the DC signal and the amplitude compared to the initial DC signal begins to increase. only it does not stop as in yours amplifying but continues beyond all bounds of the Op amps. it does not cut off at the rails either. it just amplifies to the point that i cannot even see the peaks (negative not positive). any suggestions. i would love to post a picture right now but i am on my MAc Laptop and there is not simulation software on there. as soon as i get home to my desktop computer i will post something. so hopefully my explanation would be less obscure if it is that is.

 

HAHAHA! That's outrageous! You have a serious problem with your simulator. Sorry, I've only used LTSpice. I can't help with other simulators.

__________________
You don't need a quadraphonic Blaupunkt -- you need a curve
ball.

 

well i figured i would try it out in PSpice see if it works out to be alright. but multisim is supposed to be one of the better simulation softwares out there so i am really puzzled by this. or i might just have to get a copy of lt spice.

 

These forums show that Multisim does not know if it is coming or going.
It does many things wrong.

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Uncle $crooge

 

Hey guys, anyways i tried simulating this thing once more and to no avail in multisim. I tried to build the same circuit in Pspice but i had a DEMO version and it does not allow me to connect as many nodes. I have decided to just run down to radio shack to get the components and just build the stuff. and hopefully if what burnout said to me it will oscillate properly. i do have question about the 2MEG R3 though. should i buy the resistor that will give me a gain of for or do i stick to the two MEG resistor.

another question i have for you guys is, my overall project is to build an inverter and so i decided to use the bubba oscillator as it give me greatest stability with the least distortion given the low frequency output required. i next want to amplify the wave to 120V eventually. do any of you guys have any suggestions in doing so keeping in mind that i want to achieve a pure sine wave output which is very stable and consistent.

 

LTSpice is a free download, and you can easily simulate your circuit on it.

__________________
You don't need a quadraphonic Blaupunkt -- you need a curve
ball.

 

You cannot use a sine-wave to make an inverter. Its output transistors will be a linear amplifier and get much too hot and waste a lot of power making heat.

A sine-wave inverter is made by using high frequency PWM switching for the output transistors. The low level PWM modulating signal is a sine-wave.

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Uncle $crooge

 

audio guru are you saying that me using a bubba oscillator is the wrong approach. maybe you misunderstood, i was trying to say that i was trying to construct a pure sine wave inverter as opposed to a modified sine wave inverter. i probably did wrong in my explanation.

 

You did not explain anything about your sine-wave inverter circuit so I guessed that it is just an extremely hot linear audio amplifier that wastes a lot of power making heat.

A modified sine-wave inverter is really just a modified square-wave with a step in it. Then it is still a rectangular wave but its peak voltage is almost the same as a sine-wave.

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Uncle $crooge

 

well i was just talking about my intention to eventually design a pure sine wave inverter. i was asking for guidelines as to go about doing it. i know it has to do with PWM but i just needed a more detailed explanation. meaning i knew the first step was to use an oscillator and presume the next couple of steps has to to with PWM but where do i begin.

 

You need to learn about PWM or find a teacher.

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Uncle $crooge

 

hi guys. i know i have been missing in action for a lil bit but i have risen again once more. i have a delimma with my bubba construction in that i am using a quad op amp lm348/324 and i only have one connector for the vcc. my question is how do i connect my vcc considering that the first vcc ( see bubba schematic above) take input on the negative terminal and the remaining three does so on the positive terminal. can i do this connection using just one op amp. any response would be greatly appreciated.

 

lm348 configuration is attached.

Attached Thumbnails

 

 

Connect Vcc+ to "+" voltage, adn Vcc- to "-" voltage.

I already told you your schematic was connected wrong.

__________________
You don't need a quadraphonic Blaupunkt -- you need a curve
ball.

 

Hi, ismith1984.

I am also planning to design the 12 VDC to 230 VAC inverter (500W).
So I planned to design the inverter in block by block mode.

The first block is to design the sine wave oscillator for 50Hz generation using the bubba oscillator.

Let start this as a project and share this to all in the world.