[sdiy] Dual Frequency Shifter update

[jhaible at debitel.net]

You could build your own 4200 from a quad transistor array,
of course. I think the MAT-04 data sheet has an application 
for this.

This may look complicated at first glance, but you can use
better opamps right from the start, and you need a lot of
extra stuff to make a 4Q mult from a 4200 anyway.

Better opamps: The key here is to mix bipolar technology
(lag/antilog transistors) and FETs (opamps with low
offset current - and low offset voltage, of course); I
bet you end up with something better than the RC4200.

JH.

> The other thing is, the RC4200 isn't exactly common.
> Unless someone was wise enough to grab a bunch years ago.
> I keep thinking there was a Japanese knockoff.. but I can't see it.
> 
> paul perry melbourne australia
> 
> 




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