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Old 9th April 2008, 10:30 AM   #31
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6 nV/√Hz ?
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Old 10th April 2008, 01:09 PM   #32
EUVL is offline EUVL  Europe
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We have done some more simulation and testing. Basically you can get stability for almost any gain other than +1 (unity gain buffer). But then for unity gain buffer, one might just as well use a pair of BF862 without any feedback.

For gain of -1 (unity gain inverting), we found that it is best not to use the compensation cap but just a cap in parallel the feedback resistor. Bandwidth is never a problem, always way above 200kHz.

We plan to test this in a Buffer-Filter-Buffer phono preamp with single stage gain of 100. Will take a while. Need to make and trim 4 new ones.


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Old 10th April 2008, 11:11 PM   #33
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Old 20th April 2008, 06:33 AM   #34
EUVL is offline EUVL  Europe
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> We plan to test this in a Buffer-Filter-Buffer phono preamp

While waiting for potting compound ....


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Old 20th April 2008, 06:35 AM   #35
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One more ....
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Old 20th April 2008, 04:59 PM   #36
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Bravo Patrick !!! Congratulations !!! Very very nice job really !
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Old 20th April 2008, 05:53 PM   #37
EUVL is offline EUVL  Europe
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Thanks Richard.
Was an interesting challenge and real fun to realise the design.
Hope to report on listening test in a month or so.


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Old 21st April 2008, 08:39 AM   #38
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Nice work but what the positive results be compared to using a high performance opamp? Have you ever considered to make a current feedback "opamp"? You can make those rather simple and compact also.
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Old 21st April 2008, 09:41 AM   #39
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Quote:
Originally posted by EUVL
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I love the shape of top layer - reminds me of '70s hand-drawn PCBs, just inverted :-)
Nice work, BTW
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Old 21st April 2008, 09:41 AM   #40
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by EUVL
But then for unity gain buffer, one might just as well use a pair of BF862 without any feedback.
is that a FET follower fed from a CCS that you're suggesting?
or a cascoded FET?
or what?
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