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Old 3rd May 2008, 02:46 PM   #1
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Default how to balance two operational amplifiers connected in parallel ?

As two indentical op amplifiers connected in parallel,one of them tends to be overheated due to unbalance of each IC,and any practical way to get get rid of this dilemma?
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Old 3rd May 2008, 03:02 PM   #2
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Default Balance

High power OP Amps or small signal? Basically the same applies to both. The gains have to be very closely matched, resistors of .01 to .1% tolerance in the gain loop and inputs, same for the parallel out they must have a current sharing path low ohm precision resistors, or the inclusion of a DC servo circuit.
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Old 3rd May 2008, 03:18 PM   #3
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Default Re: Balance

Quote:
Originally posted by tiltedhalo

High power OP Amps or small signal? Basically the same applies to both. The gains have to be very closely matched, resistors of .01 to .1% tolerance in the gain loop and inputs, same for the parallel out they must have a current sharing path low ohm precision resistors, or the inclusion of a DC servo circuit.

tiltedhalo,
Thanks for your prompt reply on this thread.
I am using small signal Op amps like 5532 in my modified deck`s playback circuit.It would be a great help if you could submit an explaining schematic diagram as I couldn`t get a clear picture on your posted answer.
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Old 3rd May 2008, 03:22 PM   #4
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Are you sure that the heating of one of the op-amps isn't part of the modification? Maybe it sounds better that way.

I_F
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Old 3rd May 2008, 05:23 PM   #5
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Quote:
Originally posted by I_Forgot
Are you sure that the heating of one of the op-amps isn't part of the modification? Maybe it sounds better that way.

I_F
Yes I have to admit that this combination improves all aspects of the sound qualities with the sacrifice of the adnormal over heating of the op amp that soldered on top.
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Old 3rd May 2008, 08:07 PM   #6
KSTR is offline KSTR  Germany
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Are we to assume that you soldered one op directly onto the other, in 1:1 connection scheme? If so, you're playing sort of russian roulette with them poor chips...

- Klaus
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Old 4th May 2008, 05:53 AM   #7
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Quote:
Originally posted by Mikewong


Yes I have to admit that this combination improves all aspects of the sound qualities with the sacrifice of the adnormal over heating of the op amp that soldered on top.
Actually, I was being sarcastic. I don't know who "designed" this mod that you're using, but the whole situation sounds like a case of the "the blind leading the blind".

My advice is put it back the way it was before it quits working. An unmodded device usually sounds better than one that doesn't work.

I_F
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Old 5th May 2008, 03:55 PM   #8
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Default parellel

If you could post the circuit used I can give you a better idea of what you will need. Small signal op amps tend not to be forgiving of out of balanced operation, one will most always dump current potential to the other, sooner or later one will give it up.
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Old 8th May 2008, 09:44 AM   #9
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Default Re: parellel

Quote:
Originally posted by tiltedhalo
If you could post the circuit used I can give you a better idea of what you will need. Small signal op amps tend not to be forgiving of out of balanced operation, one will most always dump current potential to the other, sooner or later one will give it up.

The attached file is taken from Aiwa XK-S9000 playback circuit.
Hoping that this circuit might help.

The IC intended to modify is 101.
Attached Images
File Type: gif xk_s9000 c_playback.gif (45.4 KB, 134 views)
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Old 8th May 2008, 12:05 PM   #10
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Default Re: Re: parellel

Quote:
Originally posted by Mikewong



The attached file is taken from Aiwa XK-S9000 playback circuit.
Hoping that this circuit might help.

The IC intended to modify is 101.
I think you are rather confused? Maybe you have read about putting DAC chips in parallel to reduce errors?

You CANNOT do this with op-amps - it would be like connecting two batteries with slightly different voltages in parallel - they would fight each other!

you could (in theory) lift up the output pin and connect (say) a 100R resistor in series with each one then joined to the load.

But what is the point? What problem are you trying to solve?
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