Can an OpAmp be built without an IC or transistor or a Vacuum tube? [closed]

Question

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.

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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.

Answer 5

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.

Answer 6

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.