[hpsdr] Differential reconstruction filter help

[Ahti Aintila]

Howard,

Instead of backward engineering your earlier "esoteric" schematic, why
not design your own filter. See this article of Jim Karki:
http://www.edn.com/contents/images/84302.pdf
I think the third-order lowpass circuit of Figure 7 and the related
math on page 154 would give you a good starting point.

73, Ahti OH2RZ


On 27/12/2007, Howard Long <hlong at btinternet.com> wrote:
> Hi Ahti
>
> > I'm not any opamp design expert, but you may see some TI's
> > fully differential amplifier. OPA1632 might be one good example:
> > http://focus.ti.com/docs/prod/folders/print/opa1632.html
>
> Many thanks for your reply.
>
> I have already used the OPA1632 in some designs, however for my purposes I
> need to use a rail-rail I/O differential opamp that operates off 3.3V to
> drive the right levels to an upconverting mixer given the PSU and power
> consumption constraints I already have.
>
> The main issue I have is that my knowledge and experience of opamp filters
> is purely 'cookbook' style I'm afraid! The schematic I referenced is a bit
> too complicated for me to attempt to reverse engineer and know how to apply
> it in a differential manner other than using the methods I mentioned in my
> OP.
>
> Thanks again for your time.
>
> 73, Howard G6LVB
>
>

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