Computing with Analog

Bil Herd shows us how you can build a calculator using analog voltages. An analog computer!

This is exactly what it sounds like. You can take two input voltages of varying levels and add, subtract, or multiply the output depending on what circuit you use as the "calculator". It's not voodoo, and it's not overly-complicated. But things do get even more fun when Bil switches over from DC to AC for the experiments.

[hallsf]

This sort of quiet continuity is so elegant. This stuff is an art form.

[rezahosseini]

Hi! This video is 7 years old but I just got a ton of inspiration from it for the project in the embedded electronic course I have in my college. Thanks a lot for this video!

[sysmatt]

Bil, I've been waiting to see more of your little analog building blocks.  Cool stuff and we def need more analog stuff like this.  Thanks -Matt

[ntesla]

Analog Devices, AD639 never to be seen again... Thanks for the video man.

[colderwar]

Love the t-shirt. I saw Hawkwind many times in the 1980's....

[PauloConstantino]

Awesome video. I really love it. Th virtual ground ground thing is because the opamp equalizes the two inputs since the output is finite. What you described is kirchoff's current law....

[waew]

Very cool video, Bil.  "Superposition" is a means of calculating the circuit response of a linear system by computing the contribution of each input separately (shorting the other input voltages), then adding the results up.  Two questions for you - what is the mfr and part number of the pin sockets you use on your building block boards?  And, same q on the tiny little 3 digit DVMs..  Cool stuff!

[edgeeffect]

I came here for the analog computer but my mind is still blown by the Masters of The Universe T-Shirt. A "dodgy" contractual-obligation compilation album but still rather a good listen.

[dualityy]

this is all very interesting and very educational and i am enjoying every moment of it.

[jfjoubertquebec]

Awesome! I'm here because I read Von Neumann's Computer and the Brain!

[cbeas]

Hi @BilHerd!
Have you ever try to do an analog memory?
Let me explain a little. Suppose than I have a black box composed by one "logic" layer based on AC and a "control" layer based on DC.
Now, this is the question.
If we have a VCO and a AFC at the logic layer, could they be controlled to maintain the frequency by the control layer giving feedback from one layer to the other and viceversa?
If we suppose that the analog values are the frequencies instead the voltages, Could it be considered an analog bit?

(sorry about my english language skill) :)
Thanks in advance!

[markchadwick]

Great setup.
However, I don’t think your explanation of “virtual ground” was sufficient. The reason the “minus terminal” is at virtual ground is because the “plus terminal” is grounded, and all opamps have 0 volts across their input terminals if operating in the linear region (i.e. not clipping). Because opamps have a very high voltage gain (approximated as infinity), the voltage across the input terminals must always be very small (approximately 0 volts). Of course the high input impedance plays also plays a role, as you mentioned.
Nevertheless, a very instructive video. Thanks.

[yazicib]

What type of breadboard is that? Where can i buy one? Looks like a pegboard but holes look like 1/2” apart instead of 1”?

[babotobati]

question for you, the numbers on the left and the right are visualised by analog or digital circuit?

[DontMansion]

Hello. Is it possible to create analog imitation of memristor?

[LydellAaron]

Extremely well done. Thank you greatly.

[seethegalaxy]

I'd be curious about the full schematic.

[BenWard]

Great video Bil. One question- is your analog multiplier the same as a VCA? For instance, after accounting for scaling, can you do the same quality of multiplication with an analog multiplier that you can with an OTA based VCA? Also- would be cool to see something about Log/Antilog amps and their uses- I know you touched lightly on it w/ your slide rule, but I'd be keen to see more. Thanks!

[josearcosgamiz]

I am curios where did you get those voltage displays?

[Death_of_Sound]

voice sounds like hank hill, and i can't unhear it