[time-nuts] Low noise power supplies - dont' use Electrolytics

Attila Kinali attila at kinali.ch
Mon Nov 28 09:07:13 EST 2011

On Mon, 28 Nov 2011 01:05:22 -0800
gary <lists at lazygranch.com> wrote:

> Ceramic caps can be microphonic. Just something to be on the look out. 
> Not so much with leaded ceramics, but more of a problem with surface mounts.

Ceramic caps have a lot of other problems too, like capacitance
derating on increasing voltage. Some types go down to 80% of rated
capacity when driven to the max rated voltage.
> Tantalums are prone to overvoltage failure. Best to really overspec them 
> regarding voltage.

Uhmm.. overspec? The rated voltage is the maximum allowed voltage.
Like something you should never cross. That's why we have these
odd numbers like 16V. They are not intended to be used at 16V but
rather at standard voltages like 12V.

> Note that some LDOs are not stable with really low ESR bypass. There are 
> app notes on this. 

Actually, the datasheet of any LDO (or power regulator) should define
the stable operation output capacitance and ESR. If you work outside
the speced range.. well.. your own fault if you get oscillation ;-)

			Attila Kinali

The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin

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