Hi all,
My new DAC+AMP is based around this simple circuit:
The DAC outputs the audio on a 1.6V bias volatge.
The design was meant to use the pot to trim out this voltage on the first opamp.
But no matter what its set to, i always get a -0.7V dc-offset on the OPA627 ouput.
This then leads to a +12V dc-offset on the LM3886's output.
Can anyone see what is wrong here?
I really dont want to put DC blocking caps after the OPA627 to fix this.
Thanks for any help.
My new DAC+AMP is based around this simple circuit:
An externally hosted image should be here but it was not working when we last tested it.
The DAC outputs the audio on a 1.6V bias volatge.
The design was meant to use the pot to trim out this voltage on the first opamp.
But no matter what its set to, i always get a -0.7V dc-offset on the OPA627 ouput.
This then leads to a +12V dc-offset on the LM3886's output.
Can anyone see what is wrong here?
I really dont want to put DC blocking caps after the OPA627 to fix this.
Thanks for any help.
Servos might help
The op amp bibles say to use a servo to control offset. There are some good notes on designing servos in these notes.
Essentially, provide negative feedback through a low pass filter -- very low pass (like 8 Hz for f0) and it will lock the output of the first stage to ground.
Be sure to use a low noise opamp in the feedback circuit, because you are applying the output to one of the inputs of your gain stage.
The op amp bibles say to use a servo to control offset. There are some good notes on designing servos in these notes.
Essentially, provide negative feedback through a low pass filter -- very low pass (like 8 Hz for f0) and it will lock the output of the first stage to ground.
Be sure to use a low noise opamp in the feedback circuit, because you are applying the output to one of the inputs of your gain stage.
Servos might help
The op amp bibles say to use a servo to control offset. There are some good notes on designing servos in these notes.
Essentially, provide negative feedback through a low pass filter -- very low pass (like 8 Hz for f0) and it will lock the output of the first stage to ground.
Be sure to use a low noise opamp in the feedback circuit, because you are applying the output to one of the inputs of your gain stage.
The op amp bibles say to use a servo to control offset. There are some good notes on designing servos in these notes.
Essentially, provide negative feedback through a low pass filter -- very low pass (like 8 Hz for f0) and it will lock the output of the first stage to ground.
Be sure to use a low noise opamp in the feedback circuit, because you are applying the output to one of the inputs of your gain stage.
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