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Old 9th April 2009, 06:50 AM   #17151
1audio is offline 1audio  United States
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Quote:
Originally posted by scott wurcer


A picoamp bias return through 22Meg, 22 micro volts DC, please, you DO understand these issues better, why be so obtuse?
Actually I don't have much of a clue what you are doing. The picoamps of bias current does help me better understand where they might be used. I read no voltage literally. Again the next question I would have is how much the temp variations will change the bias current in question. And whether it will matter.

For the uninitiated looking in, FET bias or leakage increases a lot with temperature. It can be a surprise if its not planned for. I have also seen Mica caps and Ceramic caps get very noisy in high impedance circuits when they have a bias across them. But they measure perfectly when cold out of circuit. And a hydroscopic surface contamination on a circuit board can drive you nuts. Really high impedance stuff requires a lot of care.
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Old 9th April 2009, 07:11 AM   #17152
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They appear to be 'clueless', Demian. Engineers, BAH!
 
Old 9th April 2009, 10:44 AM   #17153
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Quote:
Originally posted by john curl
They appear to be 'clueless', Demian. Engineers, BAH!
Yeah, and those Analog fellows seem to be the worst. I'll bet Scott even uses a moving magnet cartridge!

Demian, the other unexpected thing (it was for me, anyway, the first time I ran into it) is drain voltage. I had built a preamp with a FET input which had higher distortion and noise than I expected. Dropped the drain voltage by a factor of 2 and suddenly everything was OK. This caused much head-scratching, since the curves looked so nice and flat. Dumb old tube guy that I am, I had never heard of impact ionization...
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Old 9th April 2009, 10:52 AM   #17154
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Originally posted by SY
[snip] Dumb old tube guy that I am, I had never heard of impact ionization...

Really?? Where have you been hiding???

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Old 9th April 2009, 10:55 AM   #17155
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Chemistry labs.
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Old 9th April 2009, 03:23 PM   #17156
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Quote:
Originally posted by john curl
Engineers, BAH!
Here's a sample of real Engineers! Bybees for the people!

Piezobee -a very simple and cheap power filter
 
Old 9th April 2009, 03:56 PM   #17157
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For the record, Jack Bybee called me last night. He is off to Macau with his charming wife. Gambling is her thing, you know. He left the Bentley at home, but sooner or later, he promises to give me a ride in it. His new Mercedes is pretty nice, but boring at this point.
 
Old 9th April 2009, 04:16 PM   #17158
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Old 9th April 2009, 04:53 PM   #17159
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Quote:
Originally posted by syn08


Here's a sample of real Engineers! Bybees for the people!

Piezobee -a very simple and cheap power filter
Piezo horns would filter better: they have about 200 nF.
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Old 9th April 2009, 04:59 PM   #17160
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MATRA?
 

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