Hello,
It's been a a while since I posted on Headwize as topher.
Anyway, I needed to make a power supply using a switching power supply to drop voltage without wasting a lot of power, but I needed a really extremely quiet supply.
The lt3043 v regulator is good, but the switchers chop was getting through.
I went of a development of useful filters to put between them.
I had forgotten that almost all ferrite beads are made for signals with no current and
saturate with just a few mA's.
The laird 35F0121-1SR-10 was a lone surprise after a lot searching.
Says it's got a 10amp limit, but that is an overheating limit. Looks good to 100mA's.
I was able to make an astoundingly quiet supply.
To see the microvolts of noise I had to use multiple lt1028's to get a gain of 100,000 to see what was left.
The spectrum analyzer clearly saw fundamental and harmonics.
One bead ( and some caps) cut it down to just a little of the fundamental and no harmonic.
Over a thousand fold lower. After a second there was no trace of anything.
Hope this is useful.
It's been a a while since I posted on Headwize as topher.
Anyway, I needed to make a power supply using a switching power supply to drop voltage without wasting a lot of power, but I needed a really extremely quiet supply.
The lt3043 v regulator is good, but the switchers chop was getting through.
I went of a development of useful filters to put between them.
I had forgotten that almost all ferrite beads are made for signals with no current and
saturate with just a few mA's.
The laird 35F0121-1SR-10 was a lone surprise after a lot searching.
Says it's got a 10amp limit, but that is an overheating limit. Looks good to 100mA's.
I was able to make an astoundingly quiet supply.
To see the microvolts of noise I had to use multiple lt1028's to get a gain of 100,000 to see what was left.
The spectrum analyzer clearly saw fundamental and harmonics.
One bead ( and some caps) cut it down to just a little of the fundamental and no harmonic.
Over a thousand fold lower. After a second there was no trace of anything.
Hope this is useful.
