[sdiy] Analysing 4-stage RC filters without the hot air

[Timothy Daugard]

On 3/21/2016 4:07 PM, Neil Johnson wrote:
> As a worked example I used a 4-stage RC filter from Electronotes where
> I show that actually it's not that difficult at all to analyse the
> unbuffered 4-stage RC filter contrary to Bernie's protestations.
>
> Comments welcome!

I created a spreadsheet to analyze passive networks with up to 12 Ls, 
Cs, and Rs. The LCRs are both parallel and serial components in the 
network. I designed the spreadsheet years ago. I stopped at 12 because I 
never needed more in any particular design, though it would be a simple 
matter to extend the spread sheet.

I built several passive filters in cables to go between inputs an 
outputs of modules. The modules are designed with a 1K ohm current 
limited output impedance (at DC), the modules are designed to provide a 
100K impedance current load (DC) on inputs. Filters are designed to have 
an internal impedance of about 10K so that the source has no problem 
feeding filters and the modules that the filters feed don't 
significantly change the filter response.

Tim Daugard
[back to deep lurking while I work on RF and MSP430 software (and real 
work)]