At 16:41 -0500 08-03-2011, ewkeh...@aol.com wrote:
There is an interesting article in the March 2011 Electronic Products
magazine "design an ultra low noise supply for analog circuits. It is a
combination of switcher and LDO's and written by P Hunter TI so it
may also be available on their site.
This one, I presume:
<http://www2.electronicproducts.com/Designing_an_ultra_low_noise_supply_for_analog_circuits-article-fapo_TI_mar2011-html.aspx>
? Bit of a shame to use LDOs and then still drop 50% of the output
voltage. Also, Fig 2 is meaningless without a measurement bandwidth
spec.
There are other ways to get a cleaner bipolar supply from a switcher,
several of them simpler than what's shown here. You could take a
SEPIC/Cuk hybrid, or pick a switcher that allows you to trade
efficiency for switch slew rate like the LT1533. Some useful
techniques are documented in <http://www.linear.com/docs/4159>.
JDB.
[not affiliated with Linear Tech other than being a satisfied customer]
--
Years from now, if you are doing something quick and dirty,
you imagine that I am looking over your shoulder and say to
yourself, "Dijkstra would not like this," well that would be
immortality for me. -- Edsger Dijkstra, 1930 - 2002
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