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Conspicuously absent are some of the analog circuit applications. Here are three of my favorites:

1. Frequency mixer, used for heterodyning, important in radio, so I hear. https://en.wikipedia.org/wiki/Frequency_mixer

2. Log converter, where the output voltage is proportional to the logarithm of the input voltage. https://electronics.stackexchange.com/questions/374440/log-c...

3. Diode ring, which provides variable gain, used in analog compressors like the Neve 33609 (I have a clone of the 33609, and I’m very fond of it)

Think about this: if you have a nonlinear device like a diode, then the dynamic resistance changes depending on the operating point. If you modulate the operating point, you’re modulating the dynamic resistance.

Also the octaver…

https://www.geocities.ws/diygescorp/diodeoctaveup.gif

You can simulate a bunch of these (and edit too) in your browser in CircuitLab:

Diode half-wave rectifier https://www.circuitlab.com/editor/4da864/

Diode full-wave (bridge) rectifier https://www.circuitlab.com/editor/f6ex5x/

Diode turn-off time https://www.circuitlab.com/editor/fwr26m/

LED with resistor biasing https://www.circuitlab.com/editor/z79rqm/

Zener diode voltage reference https://www.circuitlab.com/editor/7f3ndq/

Charge Pump Voltage Doubler https://www.circuitlab.com/editor/24t6h3ypc4e5/

Diode Cascade Voltage Multiplier https://www.circuitlab.com/editor/mh9d8k/

(note: I wrote the simulation engine)

If you’re into audio, they can easily be used for distortion. You “clip” the top of the audio wave. Usually in a asymmetrical way, to get more pleasant sounding distortion.

Lectenna / Rectenna https://en.wikipedia.org/wiki/Rectenna

This is excellent but in typical low voltage scenarios (5V or lower) the 600mV diode voltage drop becomes very significant. Simple diode half wave rectification works fine at 100V, but at 3.3V it breaks down.

You can put a small ROM on your board with diodes, for example to store bitmaps, and for style points you can even arrange the diodes in the shape of your bitmaps: https://technologizer.com/2011/12/11/computer-space-and-the-...

You can extend the voltage doubler idea to even higher voltages with the voltage multiplier:

https://en.wikipedia.org/wiki/Voltage_multiplier

I know we're on hacker news, but let's just say I misread the title.

And here's another that's always fascinated me -> Diode Ladder Filter.

https://www.youtube.com/watch?v=jvNNgUl3al0

Btw you can try these out online with a circuit simulator

https://www.falstad.com/circuit/circuitjs.html

I'ma just leave this bad boy here.... https://www.youtube.com/watch?v=xNF891FVC6M

AJH Synth Sonic V Diode Ladder Filter. (IMHO AJH make the best eurorack filters out there..)

He mentions diode logic and points out the drawback of the limited output current, but doesn't mention the obvious solution of a transistor in voltage-follower configuration.

I always thought RTL was pretty nifty, and it was used in a lot of early computers. I think it's a lot less fussy of component values than the earlier RTL.

> The reason I put “gate” in scare quotes in the illustration is that the circuits are not readily composable to implement more complex digital logic...

Any good suggestions on resources talking about building complex digital logic out of something more suitable?

Also missing solar heating from diodes:

> This topic seems to be broadly misunderstood. It is 100% verified fact by both myself and others (including university researchers) that diode strings can produce more heat (or watt-hours, BTU) from a given solar panel than a bare resistance element.

https://www.youtube.com/watch?v=42XIbHA9Dv0

or.. detecting a nuclear event? https://www.alldatasheet.com/datasheet-pdf/view/124266/MAXWE...

Another one: Baker clamp to speed up a transistor.

https://en.wikipedia.org/wiki/Baker_clamp

Flyback diode:

https://en.wikipedia.org/wiki/Flyback_diode

A diode can switch off an AC source when a battery is present: see second circuit in accepted answer, introduced by, "Alternatively, you can probably get away with just using some schottky diodes:"

https://electronics.stackexchange.com/questions/71753/whats-...

Also, diodes can be used to provide a controlled discharge path for capacitors when a device is turned off.

The circuit in this EE StackExchange question shows it:

https://electronics.stackexchange.com/questions/471285/capac...

It has one RC constant when charging and a different RC constant when discharging through the diode.

Why would you want to charge a capacitor slowly when power is applied to the device, but discharge it fast when power is cut? There are various applications for that.

For instance, circuits that control some timed behavior, like holding a CPU chip in a reset state at start up while power stabilizes, and then releasing it. You want that circuit to reset itself quickly if power is lost.

Analog circuits have things like that in them: for instance circuits that mute an audio amplifier on power up for a bunch of milliseconds until a capacitor charges. If the power is cycled, you want that timer to reset itself.

Another application: Log amp: https://en.wikipedia.org/wiki/Log_amplifier

This exploits the diode's characteristic V-I exponential curve in amplifier feedback to produce output proportional to the logarithm of the input.

forgot adc converter! series diodes tapped at each connection.

Nice timing. I just saw pikuma's email with his new course on digital electronics and saw this here.

Current/voltage chart looks a lot like a RELU.

> ... There is a positive charge on the n-side and a negative charge on the p-side.

How completely unintuitive.