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My differential input 49830
My differential input 49830
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Old 26th March 2008, 07:41 PM   #1
Phil Olson is offline Phil Olson  United States
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Default My differential input 49830

I basically copied their schematic but added a differential input. I decided to do four pairs for possible sub amp use but would start with one pair and add them if power requirements warrant.

Alothough I have the IR FET's there I am considering the Toshiba's mentioned in the 4702 app note.

One thought I had was to drop back to two FET pairs and parallel two boards for the sub. I would just swap the differential pair of one to basically do a bridged design. That's what the BPA-300 design essectially does with seemingly excellent results.

Any suggestions for improvement?
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Old 26th March 2008, 09:44 PM   #2
SpittinLLama is offline SpittinLLama  United States
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Some of the final values will depend on the PCB layout. The compensation capacitor and gate resistors, for example. Be prepared to adjust them for full stability. The bias may also need to adjust depending on where you want to bias your design. Be sure the drain supply bypassing is close to the FET as possible.

-SL
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Old 26th March 2008, 10:06 PM   #3
Phil Olson is offline Phil Olson  United States
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Thanks! I was counting on doing some tweaking. My guess is that going from one FET pair to two or more may also require tweaking.
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Old 27th March 2008, 01:07 AM   #4
Mitch Alsup is offline Mitch Alsup  United States
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Zobel network/filter at the output.
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Old 28th March 2008, 06:20 AM   #5
Phil Olson is offline Phil Olson  United States
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Thanks, I forgot to add that.

If that's the worst of it I'll have to pat myself on the back!
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Old 6th May 2012, 12:44 PM   #6
pitone75 is offline pitone75
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Very good circuit!!!
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Old 7th May 2012, 12:38 AM   #7
djk is offline djk
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The source resistors aren't big enough to do any real good.

I would consider using an FET for the bias thermal compensation device, it will have a better tempco than a BJT for this circuit. C14 needs to be much bigger than 10pF, I would prefer 10F.
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