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Old 8th February 2015, 07:32 PM   #1
Stee is offline Stee  Italy
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Default LM3886 AS POWER BUFFER

look this project
have a special addition
a pseudo bridge with dummy load

seemingly useless
works better then classical balanced connection
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Old 8th February 2015, 08:56 PM   #2
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Have you looked at the LM3886 data sheet? It requires a minimum gain of 10 (20dB), and that output arrangement isn't a bridged connection, it's paralleled and it won't work right with only one resistor.

Mike
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Old 8th February 2015, 10:45 PM   #3
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aye, that is not going to work.
ever.

you would at least need a poweropamp (is that even a correct term??) that is unity gain stable...
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Old 8th February 2015, 10:54 PM   #4
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Apex has such a thing but I don't think you want to know how much it cost !


https://www.apexanalog.com/apex-products/pa50/
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Old 8th February 2015, 10:54 PM   #5
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See the unity gain chipamps here:


3886 T's unity gain high r.jpg

Improving the LM3886 amplifier

Improving the LM3886 amplifier



Or better perhaps, the TDA7293/4 has a pre gain stage that then connects, through external connection, to the power buffer stage. I wanted to try this but I remember some issues ...

Cheers

Last edited by AudioLapDance; 8th February 2015 at 10:57 PM.
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Old 9th February 2015, 01:02 AM   #6
tomchr is offline tomchr  United States
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The circuit in Post #5 reduces the overall loop gain to make the amplifier stable. While that certainly is a valid approach, you'll get much better performance by using noise gain compensation. NG compensation allows you to maximize the loop gain at LF while rolling it off beyond some cutoff frequency. All that's required is an RC circuit between the inverting and non-inverting inputs of the opamp/LM3886.

~Tom
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Old 9th February 2015, 05:21 PM   #7
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All that's required is an RC circuit between the inverting and non-inverting inputs of the opamp/LM3886.
Thanks to all friends
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Old 9th February 2015, 06:15 PM   #8
Stee is offline Stee  Italy
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Default That can work

maybe
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Old 9th February 2015, 06:21 PM   #9
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mmm please, tell me again why is this good in the first place ?
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Old 9th February 2015, 07:08 PM   #10
tomchr is offline tomchr  United States
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Um... You may want to re-think that 15 ohm on the output.

Here's a good app note on op-amp compensation: http://www.ti.com/lit/an/sboa015/sboa015.pdf

~Tom
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