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Old 18th December 2008, 02:50 PM   #31
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Location: San Jose
Thanks for your guys help and ideas. I thought I'd try the tech-diy matched parts, since they are actually cheaper than if bought separately from Digi-key.

Cfcubed, thank you for sharing your issues and solution with matched parts. Would it be possible to PM me with the supplier you used?

I'm also building a pair of OB speakers using MOTH drivers I got from Nelson. The combination of the F1 and the new speakers will keep me out of trouble over the holidays.

-David
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Old 18th December 2008, 03:08 PM   #32
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Quote:
Originally posted by Nelson Pass
I used the Panasonics from Digikey.

I matched the devices to .01V, and the two P channel are
matched to the two N channel. If you match to .1V for Vgs
you can trim the Sources resistors to get the offset down to
the 50 mV spec without much difficulty. If necessary, I usually
trim the P channel Source resistors, as that has little effect on
the gain figure.

I would probably buy 2X to ensure matching, and the single
current source N channel can be the odd device out of match.


Quote:
Originally posted by Nelson Pass
1 = 2, and 3 = 4. Q5 is the single current source as I recall.

I'm hoping to verify which Mosfets are matched.
* Q1 & Q2 gain devices matched
* Q3 & Q4 Upper CCS matched together

Do the gain mosfets need to be matched to upper CCS mosfets? Do all 4 devices need to be match to each other?

-David
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Old 18th December 2008, 04:44 PM   #33
cfcubed is offline cfcubed  United States
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Quote:
Originally posted by dw8083
Cfcubed, thank you for sharing your issues and solution with matched parts. Would it be possible to PM me with the supplier you used?
PM sent... Noted that my minor offset issue could have been due to other slightly mismatched/5%(?) tolerance components in my build.
No biggie as a few of those 10ohmers did the trick
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Old 26th February 2010, 01:51 AM   #34
eyoung is offline eyoung  United States
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bump again...E
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