I looked at that link and ASSume that the schematic is wrong... A 2sb747 is a to-220 power transitor, me thinks he meant the 2sb737.ricardo wrote:mediatechnology wrote:
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If I was doing more serious work on this, I would want to provide the 'floating' PSU without introducing noise into the 0.28nV input.
Paul Kemble has a link to http://www.lcaudio.com/index.php?page=8 which is essentially my circuit powered by some photocells
Anyone have experience with these photocells? There doesn't seem to be much data on them at all
I recall messing with the Leach circuit when he published it, but not that much since the powering scheme is impractical,.
Using photocells to provide floating power is interesting but I suspect there is a better way to skin that cat.
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Looking at the Kemble schematic the 1k base resistors in combination with the relatively high beta 737/786 could probably drain a floating battery in short order. Using the optical power sources they will be power limited so the circuit will stabilize at some modest voltage, I gather from some comments the typical battery for these is AA so 1.5V (or maybe 2x in series?).
Thinking out loud, instead of battery, or light power, how about driving the top and the bottom collectors with positive and negative current sources. The familiar 5 resistor and one op amp synthesized current sources should be reasonably low noise and that noise would be referenced to the output not input. There should not be a problem from running the current sources from conventional +/-15v rails. Further a servo circuit could be included detect for DC errors and balance the current sources to deliver 0V nominal output.
or not....
JR