Why is this opamp saturating?

wildswan · 13th February 2007, 02:11 AM

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

I_Forgot · 13th February 2007, 02:48 AM

Could it be because both rails are +12V as shown on the diagram?

I_F

wildswan · 13th February 2007, 03:31 AM

LOL no, that's just some messy component placement! The real circuit uses proper power rails!

wildswan · 14th February 2007, 07:10 PM

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!

wildswan · 14th February 2007, 08:30 PM

No, I'm just stupid

Had resistor in parallel with feedback cap, where it should have been in series. Hence +ve DC feedback.....

AndrewT · 15th February 2007, 05:24 PM

Hi,
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.

15th February 2007, 05:24 PM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, 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.

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13th February 2007, 02:48 AM	#2
I_Forgot diyAudio Member Join Date: Jan 2005 Location: Phoenix, Az.	Could it be because both rails are +12V as shown on the diagram? I_F

13th February 2007, 03:31 AM	#3
wildswan diyAudio Member Join Date: May 2006	LOL no, that's just some messy component placement! The real circuit uses proper power rails!

14th February 2007, 07:10 PM	#4
wildswan diyAudio Member Join Date: May 2006	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!

14th February 2007, 08:30 PM	#5
wildswan diyAudio Member Join Date: May 2006	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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