Variable resistance

[Jim Thompson]

Hello Jim,


It would have to be at least like the SD5400 in RF performance. But the
market would be small since most young EEs don't know how to design with
this stuff anymore.



That's a surprise. Usually the defense folks insist on water-tight
contracts with clauses such as the surrender of the mask plots in case
of obsolescence or breach of delivery schedule so they can go out and
have it fabbed elsewhere.

Regards, Joerg

This is a strange one... ALL documentation has been tossed, though I
did manage to scarf up a rough schematic.

...Jim Thompson

 

[Joerg]

Hello Jim,

This is a strange one... ALL documentation has been tossed, though I
did manage to scarf up a rough schematic.

That is indeed weird. Was it ever used in civilian apps? Then there
might be a higher chance of finding something at places such as
universities. There had been a number of "AM radio on a chip" ICs but
most have gone to lala-land. Some might still be used in local pagers or
hearing wands.

But it's not unheard of. Once I had to mimic the behavior of a chip as
measured on the outside but decided to do it in discretes (cheaper).
This was not reverse engineering in a bad sense but it was for the
owners of the design.

Regards, Joerg

 

[Tony Williams]

At 10:35 am
Message-ID: <[email protected]>

That was a great thread, with several conversations going on
at once, and by the 15th you had a working circuit you were
happy with, although it did have a multiplier.

Yes. Good thread. I got some very useful advice.

The circuit did not go beyond the posted breadboard,
but I think the required 0.1% spec in controlled
resistance could have been achieved with modest changes.

In fact I took the brute force route.... there was
already a computer, IEEE bus and precision DVM there,
so did a 0-10mA voltage-controlled current sink, and
'closed the loop' via a small computer prog.