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Old 13th February 2007, 02:11 AM   #1
diyAudio Member
wildswan's Avatar
Join Date: May 2006
Unhappy Why is this opamp saturating?

Hi everyone,
I've put together a wein bridge oscillator, or should be.
The problem is that the opamp keeps saturating at the positive rail.

I've removed the gain control part, from the circuit (by removing the BC182) so I'm pretty sure that it's the oscillator itself.

I can't figure out what would cause this....opamp circuits aren't my strongest point

Please help, this is driving me nuts!!

Thanks in advance
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Old 13th February 2007, 02:48 AM   #2
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Location: Phoenix, Az.
Could it be because both rails are +12V as shown on the diagram?

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Old 13th February 2007, 03:31 AM   #3
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LOL no, that's just some messy component placement! The real circuit uses proper power rails!
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Old 14th February 2007, 07:10 PM   #4
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I traced the circuit, everything is wired as it is supposed to be
I replaced the opamp (with a TL074) in case I damaged it while soldering, but no dice.

Going to rebuild. AGAIN!
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Old 14th February 2007, 08:30 PM   #5
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No, I'm just stupid
Had resistor in parallel with feedback cap, where it should have been in series. Hence +ve DC feedback.....
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Old 15th February 2007, 05:24 PM   #6
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
buy yourself a plug board to test out ideas and prototypes.
Avoids all the soldering and PCB difficulties and so easy to try different values of components.
Only 2 or 3 for a simple one.
regards Andrew T.
Sent from my desktop computer using a keyboard
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