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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: signal leads that pick up less ambient noise?
Date: Tue, 25 Feb 2025 14:45:42 +1100
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On 25/02/2025 4:46 am, Christopher Howard wrote:
> Joe Gwinn <joegwinn@comcast.net> writes:
> 
>> Google for coaxial feed through capacitors.
>>
>> .<https://www.engineering.com/the-engineers-guide-to-feedthrough-capacitors/>
>>
>> .<https://www.ketemicro.com/tec_info28.html>
>>
> 
> Thank you, I've stored these links and started looking through them.
> 
> Question: With a simple C feed through capacitor, with no resistive
> element, do you have trouble with ringing? I had thought this was a
> reason to use RC filters rather than just C bypass filter, to
> reduce/eliminate ringing.

Capacitors and resistors don't ring. Adding inductance can introduce 
ringing. but enough resistance can make the resonant circuit critically 
damped and the voltages and current will decay monotonically.

Inductor are added to give you more attentuation but they can ring if 
the tank circuit created isn't adequately damped by enough resistance 
around the tank circuit.

One cm of straight wire has an inductance of about 10nH, so bad layout 
can introduce unintended inductance

-- 
Bill Sloman, Sydney