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i am trying to make a sine wave generator. the Bubba oscillator circuit given below should produce 53 Hz. according to the text book " Op-AMP for every one", the circuit should have gain = 4, and the phase shift of 180 degrees. the values of capacitors and resistors are selected to produce 53Hz signal. everything in the circuit looks just fine to me. but when I simulate it on proteus, it has no output. what is wrong with the circuit. plus the proteus is giving some errors; pin 'V+" not modelled . screen-shot image below. this could be a simulator error, but what is the solution? In the circuit, VCC= +12volt, VEE= -12volt. Rf= 10k, Rg= 2.5k, R= 9.1k C= 0.33uF

enter image description here

enter image description here

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    \$\begingroup\$ I wouldn't take something called a bubba oscilator in a book called Op-amp for every one too seriously. \$\endgroup\$
    – Olin Lathrop
    Commented Mar 24, 2015 at 19:33
  • \$\begingroup\$ @OlinLathrop, the bubba oscillator is just a phase shift oscillator.. here..ti.com/lit/ml/sloa087/sloa087.pdf (Opamps for everyone is from TI.) \$\endgroup\$
    – George Herold
    Commented Mar 26, 2015 at 19:07
  • \$\begingroup\$ TI calls it a "Bubba" oscillator: ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf TI is has good enough "street cred" for me! ;-) \$\endgroup\$
    – Brock R. Wood
    Commented Apr 1, 2019 at 17:01

2 Answers 2

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Oscillators like this might need a little help from noise to kick start them into operation. Noise may not be modelled into your op-amp simulation so this is likely to be a possible problem. The next problem is that you might need slightly more gain than 4 - try increasing the 10k feedback resistor on U1A to 20k.

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  • \$\begingroup\$ I got your point dear, the problem could have been the absence of noise in simulation. I tried again by increasing 10k to 20k, but the result is the same. with same errors. I think I should remove the proteus simulator error first. \$\endgroup\$
    – Mehboob Alam
    Commented Mar 24, 2015 at 18:49
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I don't think it's going to work with single sided power supply.. try a split rail.
As Andy says it's sometimes hard to get oscillators to start in simulations. I've bump started them by sending a one time pulse into them.

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  • \$\begingroup\$ it is powered with +12v and -12v. and referenced to ground (zero volt). \$\endgroup\$
    – Mehboob Alam
    Commented Mar 25, 2015 at 18:26
  • \$\begingroup\$ @MehboobAlam, OK then turn up the gain... \$\endgroup\$
    – George Herold
    Commented Mar 26, 2015 at 1:24
  • \$\begingroup\$ can I change the model for 3403 op amp i.c in proteus , or update ? \$\endgroup\$
    – Mehboob Alam
    Commented Mar 26, 2015 at 18:30
  • \$\begingroup\$ @MehboobAlam, forget my answer it looks like this will work form a single supply just fine. \$\endgroup\$
    – George Herold
    Commented Mar 26, 2015 at 19:08

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