Topband: 5V 3A Wall Wart Recommendations?

Steve Harrison k0xp at k0xp.com
Tue Feb 18 01:24:41 EST 2025


On 2/17/2025 9:12 PM, Jim Brown wrote:
> Watch out for regulated PSUs, which tend to be noisy.

... Only those that use a switcher for the regulator. I've encountered
some noisy LM723 regulator chips, though; I had to use a different
manufacturer's chips to get rid of the HF oscillations they often
showed. Linear regulator ICs (three-terminal -types) also can generate
HF noise but it's easily suppressed with (usually) very small/low
voltage 0.01 uF disc or leaded ceramic caps from input and output to the
ground pin, with very short leads, right on the IC. Once inna while, a
tiny ferrite bead right on the wire soldered to the chip might be
needed, but rarely, in my experience. An oscilloscope is often a big
help to find and suppress a noisy regulator chip.

Steve, K0XP




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