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Old 18th March 2014, 08:27 PM   #1
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Default replace lm318 with lm6171

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i want to change that opamp to 6171
but i get 0.14 volts on the output causing the lm3886 to get hot
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Old 19th March 2014, 04:22 AM   #2
JohnW is offline JohnW  Hong Kong
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I suspect that the DC offset you noted is due to oscillation - the LM6171 is a high speed opamp and care needs to be taken to insure stability.

Without seeing your circuit its hard to comment further
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Old 19th March 2014, 04:24 AM   #3
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hi john i posted a picture of my circuit
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Old 19th March 2014, 05:22 AM   #4
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The LM6171 is a rocket opamp and while you can 'tame' it for audio use, you're not going to achieve that with single sided boards. For that chip I'd use a 4 layer board with an internal ground plane. Amplifiers that fast behave much better at lower impedances. Stuff you can 'get away' with in audio with slower amps won't cut it with 100MHz GBP and 3600 V/uS.

Pick a more appropriate amplifier. There are many to choose from.

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Old 19th March 2014, 05:39 AM   #5
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stratus
what would you suggest for my purpose ?
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Old 19th March 2014, 05:53 AM   #6
JohnW is offline JohnW  Hong Kong
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Quote:
Originally Posted by scrarfussi View Post
hi john i posted a picture of my circuit
You posted a PCB layout - I was referring to a schematic - but even looking at the PCB layout and the PCB tracks on the non inverting pin (Pin2) of the Opamp are far to long - with the resultant capacitance that will upset high speed opamps.
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