Analog Computer

Dabney,

A good place to look for useful integrated circuits is in multipliers and log amps.

Multipliers
http://www.ti.com/sitesearch/docs/universalsearch.tsp?searchTerm=MPY&linkId=1

Log Amps.
http://www.ti.com/sitesearch/docs/universalsearch.tsp?searchTerm=LOG&linkId=1

Hi,

I am actually building an analog computer (purely for recreational purposes - not my day job!) - it's an interesting journey through analog electronics...

For the integrators I am using TI TL081 op amps (JFET input), these together with 0.1% thin film resistors and (Russian) polystyrene capacitors make a very nice integrator circuit. Also using DG403 type CMOS analog switches rather than relays in the integrators.

You can check out what I'm doing here (caveat: some details may be missing from my circuit diagrams / notes etc as things have generally been modified during the build!): http://analog-ontology.blogspot.co.uk/

There's an excellent recently published book by Bernd Ullman on Analog Computers which is worth getting.

Peter McNair

Peter,

Thanks for sharing your results!

This is fascinating.

Didn't Burr-Brown have some analog computer circuit app notes?

Maybe someone from TI knows where those are and can post links?

To the OP - why is having an analog computer important for ion-thruster research? An 'exact' solution? Maybe a review of the device tolerances in the 50's-70's is in order. But I suppose it depends on the problem you are trying to solve.

Thanks,
John W.

Looking at the frequency with which "analog computer" crops up over the years using Google's Ngram Viewer is interesting:

Funny that the monolithic op amp chip was, I think, (μA702) created in 1963...so just when analog computers became easy to build, people stopped building them!

I've used INA128 (Burr-Brown) chips for the equality and inequality circuits.