single supply opa549

soundNERD · 15th March 2005, 01:05 AM

I want to build a single supply opa549 to run off of 12VDC.

I tried using the schematic provided by TI for single supply operation of any opamp, but when turned on, I got instant, unbearable distortion at any volume level. I thoguht it was from running at only 12V, but I tried 40V and got the same problem.

Does anybody know how to make these things run off a single supply?

Thanks!

zagisrule! · 15th March 2005, 03:44 AM

Are you using a suitable capacitor in series with the ouput to block DC? Generally over 2000uF or so....

-Matt

soundNERD · 15th March 2005, 11:41 AM

yep... even input.

At first I forgot to, but there was no DC output. When I added it, nothing happened.

Was it right to tie the Ref and the other pin (can't remember it's name) that normally ties to ground to the negative supply pin, which is connected to ground, along with the signal and speaker ground?

peranders · 15th March 2005, 11:53 AM

Can you show us the schematic?

Do the inputs float at half the supply voltage?

You must be beware of that there are special single supply opamps and there or "common" ones.

Please show us how you have done becasue this is real simple to solve.

EDIT: To your last question, no it was not right.

+U is connected to positve supply pin and ground to the negative.

soundNERD · 15th March 2005, 08:13 PM

Here is the schematic.

Thanks for all of the help.

thomas997 · 15th March 2005, 08:27 PM

Let us know how it sounds if you get it working. I want to build a sub amp with a ~26V standard transformer I have here..

thanks

soundNERD · 15th March 2005, 09:15 PM

Thomas,

That schematic doesn't work. It's the one I built that does not work.

Almost forgot, I also tied the Ref and I/LM to ground, as they would be in a normal split supply circuit.

zagisrule! · 15th March 2005, 10:43 PM

Use a voltage divider on the input of the op-amp to bias the + input to 1/2 the supply rail.

Otherwise you will only get half the audio signal out!

When the input is connected like peranders suggestion it will work, but it is vital to have input and output DC blocking caps or you will fry your source and your speaker!

Use resistors of 1K to 10K or so (even higher would work, just remember the two resistors you use must be the same value.

-Matt

zagisrule! · 15th March 2005, 10:47 PM

And by the way this will barely make any power at all, 2W or so into 8 ohms at 12VDC.

At 26VDC you would hardly have enough for a sub amp at 9W or so into 8 ohms.

-Matt

soundNERD · 16th March 2005, 12:41 AM

With peranders circuit, I also connect 12VDC to the power pins not just where it shows right?

And I still don't know what to do with those ref and I/lm pins

15th March 2005, 01:05 AM	#1
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	single supply opa549 I want to build a single supply opa549 to run off of 12VDC. I tried using the schematic provided by TI for single supply operation of any opamp, but when turned on, I got instant, unbearable distortion at any volume level. I thoguht it was from running at only 12V, but I tried 40V and got the same problem. Does anybody know how to make these things run off a single supply? Thanks!

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15th March 2005, 03:44 AM	#2
zagisrule! diyAudio Member Join Date: Apr 2004 Location: Edgewood, NM	Are you using a suitable capacitor in series with the ouput to block DC? Generally over 2000uF or so.... -Matt

15th March 2005, 11:41 AM	#3
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	yep... even input. At first I forgot to, but there was no DC output. When I added it, nothing happened. Was it right to tie the Ref and the other pin (can't remember it's name) that normally ties to ground to the negative supply pin, which is connected to ground, along with the signal and speaker ground?

15th March 2005, 08:27 PM	#6
thomas997 diyAudio Member Join Date: Feb 2004 Location: Vancouver	Let us know how it sounds if you get it working. I want to build a sub amp with a ~26V standard transformer I have here.. thanks

15th March 2005, 09:15 PM	#7
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	Thomas, That schematic doesn't work. It's the one I built that does not work. Almost forgot, I also tied the Ref and I/LM to ground, as they would be in a normal split supply circuit.

15th March 2005, 10:43 PM	#8
zagisrule! diyAudio Member Join Date: Apr 2004 Location: Edgewood, NM	Use a voltage divider on the input of the op-amp to bias the + input to 1/2 the supply rail. Otherwise you will only get half the audio signal out! When the input is connected like peranders suggestion it will work, but it is vital to have input and output DC blocking caps or you will fry your source and your speaker! Use resistors of 1K to 10K or so (even higher would work, just remember the two resistors you use must be the same value. -Matt

15th March 2005, 10:47 PM	#9
zagisrule! diyAudio Member Join Date: Apr 2004 Location: Edgewood, NM	And by the way this will barely make any power at all, 2W or so into 8 ohms at 12VDC. At 26VDC you would hardly have enough for a sub amp at 9W or so into 8 ohms. -Matt

16th March 2005, 12:41 AM	#10
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	With peranders circuit, I also connect 12VDC to the power pins not just where it shows right? And I still don't know what to do with those ref and I/lm pins

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