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Chip Amps Amplifiers based on integrated circuits

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Old 15th March 2005, 09:30 AM   #11
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Quote:
Originally posted by Matttcattt
The buffers, or all the opamps?
Quote:
Originally posted by richie00boy
output of each op-amp that will drive a cable
So that would be the buffers then.

Quote:
Originally posted by Matttcattt
Which filters? The lowpass?
Quote:
Originally posted by richie00boy
for your sub low-pass as well instead of using a 0.22uF
It would seem so.

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Old 17th March 2005, 08:45 PM   #12
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I dont apear to have read you reply very well.

Thank you for your advice.

I'd better get on with building them...

[edit]: I've updated the diagram to check i've got the right idea.
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Old 17th March 2005, 09:55 PM   #13
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Quote:
Originally posted by Matttcattt
I've updated the diagram to check i've got the right idea.
For the summing op-amp I would use lower value resistors (like 22k).
You have an input buffer now.
Also, you will optimize dc-offset if instead of connecting NI directly to ground you use a resistor.
That resistor value should be the parallel combination of the other three resistors.
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Old 18th March 2005, 07:13 AM   #14
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Agree with that. Also I'd put the 100 ohm resistors on the outputs of the left and right lines as well. 22k would also be a good value of input impedance for your new input buffers.
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Old 23rd March 2005, 12:28 AM   #15
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Ok, i've made some changes, and ringed them as the diagram is quite large... Is everything i've changed ok?

[edit]:forgot the image...
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Old 23rd March 2005, 07:29 AM   #16
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Looks good but those 10k resistors on the output to ground are redundant.
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Old 23rd March 2005, 06:02 PM   #17
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Quote:
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Looks good but those 10k resistors on the output to ground are redundant.
No, they are not redundant.
The chips need a path to ground when there's nothing connected on their outputs.
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Old 23rd March 2005, 06:08 PM   #18
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Why is that Carlos? In the dozens of such circuits I have built it has yet to appear a problem. Sure the input if floating needs them to provide bias current, but I don't see why the output needs them.
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Old 23rd March 2005, 06:34 PM   #19
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Quote:
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Why is that Carlos? In the dozens of such circuits I have built it has yet to appear a problem. Sure the input if floating needs them to provide bias current, but I don't see why the output needs them.
The output should not be floating, as it will if there's no device connected.
It needs a return path.
Just try what happens when an op-amp has it's output(s) floating. Touch the op-amp with your finger and feel the heat.
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Old 23rd March 2005, 06:37 PM   #20
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What heat? I've never noticed any.
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