[sdiy] Leapfrog (was: Re: Cauer Filter Design)

[Glen]

At 02:09 PM 1/6/04 , jhaible wrote:

>I still hesitate to build a circuit where the signal would run
>thru
>50 or even 75 opamps. Not sure how the ever so tiny unwanted side effects
>of an opamp will add up in a long signal chain. For *that* application, I
>guess
>it's easier to just use 25 cheap inductors.

It's my understanding that the version with the inductors requires a fair
amount of "post amplification", is that correct? Does the version using
opamps avoid the massive signal loss of the inductor-based approach? If so,
there might be some merit in the opamp approach after all. It might help
preserve the S/N ratio better than the inductor approach. 

It should also be much more immune to magnetic interference, compared to
the inductor version, and might be less susceptible to hum pickup. 

If built with surface-mounted quad opamps, I wonder how large the circuit
would actually be? It actually fit on a reasonably sized circuit board.

Would the op-amp version of the filter be more accurate? What are the
tolerances of the inductors you used, versus the tolerances of the
components that would be used in an opamp version?

If you ever finish the design of the opamp version, please let me know. I
think I want to try building it! Remember, the most "sane" projects aren't
always the most interesting or fun projects.  ;)


later,
Glen Berry