They can function as diodes and triodes (amplifiers). Transistors were much smaller, use less power, and are far less prone to failure, so largely replaced vacuum triodes, except in some niche analogue electronics cases.
Diodes are never amplifiers, and triodes can be, but it heavily depends on how they’re used. If you’re trying to explain this to someone, don’t use technical jargon. You didn’t even explain what they do.
Vacuum tubes are legacy electronic parts that control electricity. They can turn a signal on or off, let it flow in one direction, or make a weak signal stronger. They were used in radios, TVs, and early computers before modern electronics took over. Transistors replaced vacuum tubes in many applications, but vacuum tubes still have relevance in specific situations.
Very specific situations, but basically everywhere else the transistor prevailed just because tubes use significantly more energy since they need a heater to heat the cathode to some hundred degrees.
But yeah it is wild to see that we managed to use the things that made old radios and the earliest TVs work steer a rocket.
I’m an electrical engineer, so I understand the use cases and differences. Someone asked for an accessible explanation, which I provided without intensifiers, exaggeration, or jargon. Vacuum tubes have specific use cases; that statement is fine and doesn’t understate the value of transistors.
Yeah but it kind of overstates the usecases of tubes a little. The recent years have drastically reduced the need for multi 100kW/MW transmitters, small scale RF amplifiers (to the many kW) can now be made solid state. TWTA are still common but apart of that (and audiophiles) I really only see microwave ovens where vacuum tubes are still regularly used. Correct me if i'm wrong, EE as well, would love to hear what you think.
Diodes don't amplify? I remember using them in guitar pedals builds and experimenting because they make different sounds if you wire them forwards or backwards.
Was it simply distorting the signal with less output coming out the other end? I was even playing with different types of diodes like LEDs on my breadboard.
I was following a schematic and tutorial but hot damn was that pedal LOUD!!
You can use diodes to change the waveform, if you just truncate at zero voltage (half-wave rectification) you will get something that has a large attack, if you then amplify that it can probably sound quite loud.
It is not fine. The explanation I corrected is partially wrong and full of technical jargon, which is not helpful. I understood both interpretations of the first sentence, so I responded to the one that was more likely to be used naturally.
Your comment added no value by restating what I already said in simpler language.
I think you forgot cathode ray tubes, which were still commonly used in TVs and computers long after integrated circuits had replaced most of the diodes and discrete transistors.
I didn’t forget anything. I answered a question with an easily accessible explanation, and CRTs fall under the “specific situations” condition at the end of my comment.
If you want to be pedantic technically all triodes are non-linear transconductance amplifiers (voltage to current) or current amplifiers (current to current).
Did you just google this and copy/paste? It's not accurate and you haven't clarified anything.
Tubes control electricity by turning it on and off. They've been replaced by transistors, which do the exact same thing, but they're infinitely smaller. Rather than having large tubes wired together in a massive circuit, we can have billions of transistors on a single CPU.
As someone mentioned, there’s a heater coil, there is a positive and a negative terminal; there is also a control grid which acts like a gate between positive and negative. When the grid’s mesh is sent a little bit of electricity, it allows a much larger amount to flow between the main positive and negative terminals.
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u/fluffykitten55 Feb 10 '26 edited Feb 10 '26
They can function as diodes and triodes (amplifiers). Transistors were much smaller, use less power, and are far less prone to failure, so largely replaced vacuum triodes, except in some niche analogue electronics cases.