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Is it possible to build an OpAmp without using an integrated circuit or a transistor or a vacuum tube? I wanted to see how it would look on a larger scale before miniaturization on a chip.

I was hoping for a high view of what that would entail, not only that it is logically possible.

@HarrySvensson Thanks. That is what I wanted. I didn't mean to cause a ruckus. I only wanted to see what was going on outside of all the YouTube videos and all the rest. I figured if I could see it with big chunky non-IC parts, I could understand it. Apparently I miscalculated there.

What I should have asked for was an equivalent circuit. Now I know the keywords to search and have found many.

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closed as unclear what you're asking by Scott Seidman, Chupacabras, Bimpelrekkie, pipe, dim Sep 13 '18 at 11:51

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ No, you need something active to deal with feed back into the circuit. \$\endgroup\$ – CrossRoads Sep 12 '18 at 16:37
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    \$\begingroup\$ You could probably make a semiconductor using wood if you really tried. It probably wouldn't be wood when you finish though \$\endgroup\$ – BeB00 Sep 12 '18 at 16:39
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    \$\begingroup\$ @BeB00 You might want to patent the process :) \$\endgroup\$ – Eugene Sh. Sep 12 '18 at 16:40
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    \$\begingroup\$ I think I understand what OP really wants, he just explained it very bad (I think). If OP wants to understands how OP-amps works, then maybe OP should play around with a simulator. \$\endgroup\$ – Harry Svensson Sep 12 '18 at 17:28
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    \$\begingroup\$ @HarrySvensson Thanks. That is what I wanted. I didn't mean to cause a ruckus. I only wanted to see what was going on outside of all the YouTube videos and all the rest. I figured if I could see it with big chunky non-IC parts, I could understand it. Apparently I miscalculated there. \$\endgroup\$ – johnny Sep 12 '18 at 17:34
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I think I understand what OP really wants. If OP wants to understands how Op-Amps works, then maybe OP should play around with a simulator. In this particular online simulator, OP can actually see the current and the voltages and how everything behaves. Things which are difficult/tedious/impossible to do without an oscilloscope or other measurement devices.

After you've clicked the link, then you can browse many other Op-Amp designs under circuits > Op-Amps.

The one in the link was the circuits > Op-Amps > Amplifiers > Inverting amplifier.

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    \$\begingroup\$ I think I understand what OP really wants And you have my respect for finding out what OP was really asking because this was a very poorly asked question. \$\endgroup\$ – Bimpelrekkie Sep 12 '18 at 18:49
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    \$\begingroup\$ @Bimpelrekkie Part of learning is learning what you don't know what to ask for. \$\endgroup\$ – johnny Sep 12 '18 at 19:29
  • \$\begingroup\$ @johnny Don't forget to watch this video by Dave Jones. It certainly helped me when I was where you are now. \$\endgroup\$ – Harry Svensson Sep 12 '18 at 19:46
  • \$\begingroup\$ @HarrySvensson I clicked that Dave Jones video half expecting to find an introduction into how to be more emphatic and aware of cues on what people want. Clearly you are skilled in that, too. :-) \$\endgroup\$ – Prof. Falken Sep 13 '18 at 11:32
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    \$\begingroup\$ @Prof.Falken Online I may be that, in real life I'm struggling ;) \$\endgroup\$ – Harry Svensson Sep 13 '18 at 11:57
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Opamps have power gain, so one way or another you need a external power source and active components. You have ruled out the usual active components used for amplification in electronics, which are transistors and vacuum tubes.

You therefore need to get clever and find other ways to amplify. That means you need to be able to control a large amount of power by variations of a small amount of power. Some possibilities:

  1. A motor driving a rheostat.

  2. LEDs controlling LDRs (light dependent resistors).

  3. Pressure-controlled water flow valves.

  4. Pressure-controlled pneumatic valves.

  5. A gasoline engine with the control being the throttle.

  6. A mechanically controlled adjustable transformer, like a variac.

  7. A electrical generator where the power input is the mechanical rotation of the shaft, and the control is done by changing the field winding current.

Once you have something that can amplify, you still have to use it, or several of them in the right configuration, to make a opamp. This is just like a transistor isn't a opamp, but multiple transistors arranged the right way (with some passive parts) can be a opamp.

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In principle you could design and build an op-amp with magnetic amplifiers or one that operated mechanically. Amplifiers are amplifiers, so at a high level they'd be designed on identical principles. The devil, of course, would be in the details.

Mechanical analog computers have been around for centuries, and mag-amps pre-date vacuum tubes and silicon ICs. The literature on them is mature, and designing an op-amp with these technologies could be done.

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The US Navy used magnetic amplifiers to servo the aiming points of 16" guns even as the battleship underwent mild roll/pitch/yaw.

I recall the power levels were 100,000 watts or about 1,500 horsepower.

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You could always build circuits using fluidics. You would use hydraulic fluids instead of electrons, and it was a hot research area before the integrated circuit was invented.

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  • \$\begingroup\$ You still need to interface it to electrical system. \$\endgroup\$ – Eugene Sh. Sep 12 '18 at 17:32
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    \$\begingroup\$ No, the OP didn't say anything about an "electrical" system. \$\endgroup\$ – Elliot Alderson Sep 12 '18 at 17:39
  • \$\begingroup\$ Opamp is an electronic component by definition. \$\endgroup\$ – Eugene Sh. Sep 12 '18 at 17:40
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    \$\begingroup\$ I disagree. An operational amplifier is an amplifier that is reasonably used to perform an operation, serving as the basis for some form of computational device. The OP didn't say anything that restricted the question to electronic devices, and it seems that some other contributors agree with my broad definition of the question. \$\endgroup\$ – Elliot Alderson Sep 12 '18 at 17:45
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    \$\begingroup\$ Well, my definition is a common definition that appears to be shared by (at least) Olin and schadjo so maybe the question is not about your definition. \$\endgroup\$ – Elliot Alderson Sep 12 '18 at 17:54
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I'm not sure why you would want to do this, but there is a reason op amps are used so widely with chips.

You could build one with vacuum tubes or transistors. But the problem is even two components like that of the same model can have pretty varied functionality, and it changes with temperature.

One advantage of an op amp on an IC is that (1) the components are more likely to be very well matched, since they are on the same die, and (2) they are at exactly the same temperature. Look up "long-tailed pair", a classic op amp input design, which takes advantage of these.

If you are wondering why you don't see op amps that aren't on a chip, or at least a couple of (matched) transistors, the answer is that op amps became far more practical to build with the coming of analog ICs. If you are asking is there some way to build an op amp (equivalent) without silicon involved, people have given some ideas above.

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