Re: analog multiplier help


theJackal wrote:
> On 19 Dec 2005 08:57:46 -0800, bill.sloman@xxxxxxxx wrote:
>
> >
> >theJackal wrote:
> >> On Sun, 18 Dec 2005 11:26:16 +1100, Adam S
> >> <a_seDELETEycUPPERCASEShelLl@xxxxxxxxxxxxxxxx> wrote:
> >
> ><snip>
> >
> >> With an integrated product you don't know whats in there and normally
> >> that makes me feel uncomfortable.
> >
> >Barry Gilbert of Analog Devices has published a number of papers on
> >"Gilbert cell" mixer's and multipliers.
> >
> >A search on "Gilbert B." + translinear on scholar.google.com picks up
> >some 28 references.
> >
> >You should be able to get pretty fair idea of what goes into the Analog
> >Devices mulitpliers if you read a few of them. More than enough to make
> >you feel comfortable, in my expereience.
> >
>
> Ummm....
> Reasons why I prefer discrete components.
> 1) A designer should be familiar with discrete circuit disegn
> techniques , something he/she loses when using integrated circuits.
> 2)You compromise circuit flexibility when you use an integrated
> circuit
> 3)Discrete communication circuits are superior to integrated circuits
> in performance.
>
> ><snipped bad advice>
> >
> Your Proof?
> I disagree.
> Its a well known fact that MOS/FET are superior to BJT mixers.

For what frequencies?

> Try reading something on that.

Such as?

My impression is that the virtues of dual gate MOSFET mixers have
everything to do with the good behaviour of the components at
relatively high frequencies.

The OP wants good mixing - and explicityl wants to minimise spurious
high order product spurs - at frequencies up to 10MHz, A well
compensated Gilbert cell multiplier will do much better than a MOSFET
for this sort of job. He also wants to use fairly high level signals,
which won't work well with a dual -gate MOSFET mixer.

The numbers for the MOSFET would have come from "Transistor Circuits
and Applications" (Prentice-Hall series in electronic technology) by
Laurence G Cowles ISBN: 0139300732.

The ISBN is for the second edition from 1974 - I had the first edition,
until it got soaked when a pipe froze in Cambridge U.K. some twenty
years ago.

-------------
Bill Sloman, Nijmegen

.

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