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.
A device used to multiply two analog signals in time domain. Best known for the sound of the Daleks in the original 1960s Doctor Who series. Has some applications outside of music and sound effects. If you can find those old fashioned audio transformers, this effect does not require a power source.
Two diodes in parallel with opposite polarities. Clips the incoming AC signal to a +/- diode threshold voltage. Put a high voltage gain amplifier stage in front of it and you get the classic electric guitar distortion tone you know and love. Allegedly works best with germanium-unobtainium diodes. In their absence, using two different kinds of diodes can also have pleasant tonal qualities.
So many distortion pedals use an op amp to run a signal into antiparallel diodes to create distortion. I’ve spent a few weeks trying to emulate it, and it’s a lot of fun.
Different flavors of diode make significant changes to the way it sounds. Even things like LEDs can be used (they are Light Emitting Diodes, after all).
Andy Simper of Cytomic is some kind of mad genius at this stuff. He’s created a painstakingly accurate emulation of the Ibanez Tube Screamer that allows you to change the values of basically every component in the circuit diagram. It’s jaw dropping: https://cytomic.com/product/scream/
He’s also shared a ton of incredible information about how he emulates circuits. The math can get really intense. If anyone is looking for a fun project, I strongly suggest experimenting with circuit modeling. It’s a great workout for the brain.
Abuse minority carrier lifetime to very suddenly turn from resistive to capacitive just after switching from forward current to reverse bias; use the fact that the current wants to keep flowing to force it to concentrate into another step recovery diode that's about to cut out, in turn making the cut off spike even sharper, and on.
Surprisingly capable for e.g. blasting a FET gate off while tanking the Miller effect gate current needs through sheer power of SRD-based-pulse-shaping.
Because for e.g. GaN and SiC if you have to choose between ZVS and ZCS, you can take ZVS and just furnish a gate pulse that _makes_ the channel remain off as the current drops and the voltage soars. At least if you pull some tricks and make the current commutation loop sufficiently low inductance to keep your transistors from blowing out in self-inflicted overvoltage due to a current that needed to pass too high an inductance in too short a time.
(Total drain charge is sadly fundamental to the channel's existence, and non-ZVS turn-on is unavoidably lossy. A majority carrier device is theoretically capable of just switching off though if you can arrange the structure for extremely low inductance.)
> 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)
I just had a quick look at the service manual, but isn't that more of a diode bridge than diode ring? A Ring Modulator has the diodes connected nose-to-tail in a ring, but the gain cell in the 33609 looks more like a rectifier :-)
You can see the same circuit in the VCF and (incorrectly drawn) in the VCA of the Korg MS50 synthesizer. In the former it acts as the "variable resistor" in a fairly straightforward Sallen-Key lowpass filter (there are two feedback capacitors, one to either side of the bridge, to attempt to prevent the input voltage also tuning the filter). On the VCA the diodes are drawn wrong but the pin numbers are correct.
For log converters you should not use diodes, because their parasitic currents mask the current component that has an exponential dependence from the voltage.
For log converters, bipolar transistors are used, because their collector current depends only on the ideal diode current of the base-emitter diode, not also on its parasitic currents, so the base-emitter voltage has a logarithmic dependence on the collector current, for a relatively wide range of currents.
Yeah, I remember one of these my brother cooked up to power a He-Ne laser tube way back when... It was lots of fun to apply to other off-label experiments too.
Diode ladder, but also in various Sallen-Key designs like the Steiner-Parker Synthacon which we all now know from the Arturia Minibrute (Yves Usson probably made more of these filters than Nyle Steiner ever did!) and as I've mentioned elsewhere the Korg MS50. I think the Yamaha GX1 filters used a diode bridge too, probably using discrete transistors similar to the Korg 700S filter.
I did this once with a diode when I was a baby electrical engineer in college. But of course you need some kind of measurement circuit. So somehow(???) I figured out I could wire a diode into one axis of my analog Gravis joystick--hooked up to my soundcard--and get a fairly accurate and stable measurement of temperature by poking the monostable multivibrator (pretty sure that's what it was called) in the soundcard that would trigger the time it took to drain a set amount of charge through the joystick's x-axis/now-diode.
Novices who don't have a clue nor know any better come up with the weirdest solutions. I have no clue whatsoever now what inspired me to even try something like that.
Kinda interesting to hear about. I have a 500 chassis I’m slowly working on filling. I’m between the RND 535 or 543, and had never heard of a diode bridge comp before looking at the 535.
I have the Heritage HA-609A. I considered going 500-series. Maybe some day in the future. For now, I have two preamps and the HA-609A in a 4U rack, and most of my other gear is in storage. Keeping things light.
Looks great! Would you have a recommendation for intro materials to help me learn the basics of electronics using CircuitLab? I have a working understanding of signal processing but building an actual circuit without electrocuting myself, not setting my Raspberry Pi on fire, or selecting the right set of components for the simplest DIY project based on spec sheets are a mystery to me.
A favorite of mine and one of the most common ways to generate a pretty high voltage DC. The full wave version pairs well with a center tapped secondary of a resonant transformer.
In some early computers, the bootstrap was actually a matrix of diodes where you'd remove a diode to get a one and leave it in for a zero. I had a bunch of these boards sometime in the mid 1970's and found you could program a fully populated board with a 9V battery - basically connect it across a diode in a bit position where you wanted a '1', there would be a small but pretty flash from inside the glass case as a zero turned into a one.
When things like the 74S188 were available, we had so much fun squeezing bootstrap code for PDP11's into 2 of them; 32 words by 16 bits was more than enough (later I got code that would boot five different devices into 256 words).
The description of forward current and the graph are completely wrong. The graph shows approximately linear current above 600 mV, and the text says "When the threshold is cleared, the diode admits current that’s roughly proportional to the “excess” applied voltage, an ohmic behavior that’s a consequence of the resistance of the material itself".
The current through a diode is exponential with voltage, not "proportional". The graph shows 1.6V applied to a diode yielding 250 mA. In reality, this isn't possible since you'd get a huge current and destroy the diode.
The Wikipedia equation there mentions the formula ignores the contribution of the internal resistance, which would make it proportional. It seems the article assumes that resistance is a significant contribution (possibly even just from their voltage source) while you assume it is not, for any given particular diode being evaluated or measured, either could be right
> Internal resistance causes "leveling off" of a real diode's I–V curve at high forward bias. The Shockley equation doesn't model this, but adding a resistance in series will.
For small diodes and all LEDs as far as I know, it will level alright. Leaving behind a cute little smoldering crater where the now vaporized diode used to be.
Take this very generic diode here. When mounted as instructed for the highest heat dissipation, it should gain 50°C per Watt. The flattening of the Current-Voltage curves starts at around 1A. As the diode heats up, the resistance lowers. Extending the limits.
Maximum before damage is 150°C. Minus 25°C ambient leaves us 125°C. Divided by 50°C/W gives us 2.5W. Around 2.8A-3A at 0.8V-0.9V forward voltage.
But the curve is barely proportional at 5A. You might also notice that the datasheet doesn't provide numbers beyond that point. Presumably because the diode left the room then.
> The diode is given neither the mathematical rigor of linear circuits nor the red-carpet treatment of the transistor
Sedra/Smith dedicates Part I chapter 4 (pages 174-229 in the 7th edition, not counting the exercises) to diodes. That's longer than chapter 5 (MOSFETs) or chapter 6 (BJTs), and a substantial portion of chapter 3 is devoted to pn junctions. "The Art of Electronics" by Horowitz & Hill dedicates less space to diodes, but it's also much less mathematically rigorous. And they have you building radios & diode mixers before they introduce any sort of transistor. So I'm not sure I agree with this line since neither of the two most popular university electronics textbooks really fits that characterization. It's definitely true of many online electronics "tutorials" though.
Thank you. I was on the fence posting my comment earlier but I’m glad I’m not the only one who is tired of blog posters leading a subject with a blatantly false statement.
I have used some regular diodes today as a way to lower the input voltage and this case is not covered. A diode might be more effective than a buck converter because all I wanted was to have a 0.7V lower voltage and the converter can not work in this condition. Zener diode can but it dissipates too much heat for high-current application.
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.
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.
The N side has negative charge carriers. It has a positive charge in the depletion region because the charge carriers are missing. Likewise, the P side has positive charge carriers, and when they’re missing, you get a negative charge.
This is true whether we live in the current universe or live in an alternate universe where we say that electrons have positive charge. The depletion region is where the charge carriers are missing (depleted), so you get the opposite charge of whatever the charge carriers are.
> 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.
> 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.
In some of my early experiments with little radio transmitters some 30-odd years ago I managed to burn my fingers to an astonishing degree with little plastic transistors like ZTX300s and BC548s.
I remember my late father also commenting around that time "How come a 2N3866 which is rated for a couple of watts can get so hot it melts all its legs off when it's running off a half-flat PP3 battery?", astonished as yet another 2N3866-based amp got a bit lively and melted its legs off despite only running off a half-flat PP3 battery.
So yes I can believe a string of diodes would be a more effective heater than a resistor.
At the cost of very efficiently radiating that heat back out into space at night.
Making electricity and then using that electricity to heat something elsewhere lets you insulate, effectively allowing you to create a box that heat energy can only pass one way.
We have a one-way diode technology for heat, it's called "glass", and it'll bump your efficiency by about 25% versus uncovered flat plates on a still day. More in windy conditions etc, lots of hand waving assumptions about spherical cows in a vacuum etc.
You'd need some kind of storage for the heat, something with a large thermal mass that doesn't readily give up it's heat to the surroundings. Sand or water or even big rocks or a thick slab of concrete.
I suspect (didn't watch) it's just that a diode makes a crude MPPT tracker (since a PV array is just a bunch diodes arranged to collect photons at the P-N junctions). The benchmark is probably "non-variable resistor".
For people who don't know much about solar panels mystified about this:
Solar panels are not ideal voltage sources, their internal impendance varies depending on temperature and the amount of light falling on the panels. Because the point of maximum power in the circuit is achieved when the internal and external impendances are matched, a simple resistive circuit is inefficient and results in the panel converting less light into electricity. If you had a variable resistor, you could adjust it over the day to match the panel, but it is of course easier to use a semiconductor device that does this for you. Any halfway decent battery charger setup or PV inverter has one, but if you are building your own heating system, just stringing together a bunch of diodes might sound stupid, but totally works.
my thought was that a diode removes all the current from its voltage drop (aka: why your LED will burn out if it gets uncontrolled current). A resistor will never remove all the current going through it.
Maybe we're saying the same thing in different ways.
Back in the oldschool days in the 1990s, I remember our
school had soldered diodes, that is, we pupils had to
do so manually. That was quite fun. Unfortunately I
haven't quite had a need or use case to do so again;
I tried to get into arduino, but I found it too much
needing self-learning. With that I mean I'd have to
understand a lot in order to do something useful. I have
no problem with learning something new, but my time is
super-limited these days and I need to prioritize hard,
so I kind of gave up. Perhaps I try for Raspberry Pi
but I am afraid it will also require a lot of time
investment before it becomes "useful" (aside from learning
something new, which is always useful, but other things
also need to be learned, so time is of limited value here).
Is (like the article said) this information really not taught in electronics curriculum anymore? It's been a while since I was in school, but this was all covered in my undergrad EE 2XX/3XX classes. Do modern designs use fewer diodes and more ICs in their place?
I’m sure it is still taught, but a lot of power designs do often now swap diodes out for actively controlled mosfets, for example in power multiplexing (there are integrated chips called ‘ideal diodes’ or eFuses which use mosfets that do it all for you), or swapping the diodes in DC/DC converters with mosfets (called ‘synchronous rectification’).
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:"
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.
I had a friend in high school who brought in the Tesla coil he made with among other things a PSU from an old computer.
I pestered that kid so hard about DC-DC voltage regulators and he did not know enough electronics to design one from first principles. I think ladder circuits was as far as he got. But I wanted step-down not step-up transformers.
15 years later when the first gen of really good LED flashlights with built-in voltage regulators popped up I owned at least one at all times.
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.
I've been looking for something to do with the bag of 1N4001 diodes I trash-picked decades ago. There are 1,000 pieces minus the dozen or so I've used in projects. The 50V PIV and slow switching speed limits their application, but I have a lifetime supply!
> 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?
While diodes alone are not suitable for complex logic, they were instrumental on making computers cheaper in the late vacuum tube era. Vacuum tubes have fairly low reliability and short usable life so having too many of them in your computer is really bad for the cost and reliability of your system. Early transistors were not much better. They would get better over time, but cheap, reliable mass produced diodes were available long before transistors got there.
And while diodes alone cannot do it, a system with a few vacuum tubes to provide the gain and driving a whole lot of diodes made a lot of computers possible at price points that vacuum tubes alone could only dream of. An example is the hacker folklore sweetheart LGP-30, of The Story of Mel fame. 113 vacuum tubes driving 1500 diodes made for a computer that was the size of a fridge, weighed 800 pounds, drew 1.5kW and cost $50k (~500k in modern money), which made it pretty much a personal computer for the late 50's.
They might be referring to RTL (resistor-transistor logic). A transistor in the circuit can maintain the same output current that was input. (A transistor in fact a diode and a half.) RTL was superseded by TTL (transistor-transistor logic) but, hey, the Apollo computers that put astronauts on the Moon used RTL logic.
You could start with the late Don Lancster's book [1].
I have a little "breadboard helper" that I am wrapping up (that includes a project manual) for creating RTL circuits and others [2]. (I hope to sell a few.)
Not present and ultimately-cursed - using LEDs not only as bridge rectifier but also as the voltage drop for power conditioning before going into a processing IC.
That's exactly why it's called a 'rectified' linear unit! It's a half-wave rectifier. The ReLU function is just what you'd see if you put an (ideal) diode on a curve tracer.
(Although to be more accurate, it would be what you'd see on an I-V curve tracer if you measured an ideal diode in series with a 1-ohm resistor. The diode by itself would just go vertical at the Y axis, and the ML people would mutter into their beards about exploding gradients.)
Yes, because the slope of current versus voltage goes infinite as soon as the voltage goes positive. The math would explode, and so would the diode, given enough current.
> The diode might be the most neglected component in the electronics curriculum today.
Nonsense like this is why I don’t read lcamtuf. His “electronics 100” falls short of any standard-issue books - today and in the past. And you can open any of them up and very often the very first thing they discuss is the Diode, not only because it’s an “easy” case to begin understanding semiconductor materials (as opposed to tube diodes), but because it forms the basis of understanding more complicated semiconductor devices and why they work the way they work.
I’ve been wholly unimpressed by lcamtuf’s output on this subject because he’s trying to teach but doesn’t know how. He’s trying to come across as smart but his covering of the subject matter is dwarfed by someone like Forrest Mims, which is amusing to think about.
Pick up a book by someone like Melvino or Floyd. They cover analog, digital, computer systems, all sorts of shit. Even the old NEETS books along with technician manuals are a godsend. NEETS approach is particularly good because it moves between phenomena and application in a broad spectrum, which is what helps for concepts to stick.
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.
4. Varactors! https://en.wikipedia.org/wiki/Varicap
Reverse biasing a diode at different levels changes the junction capacitance. Also used in radio, for things like variable filters.
edit: oh, it's topped pinned comment!
Two more from the world of analog music/guitar electronics:
1) Ring modulator: https://en.wikipedia.org/wiki/Ring_modulation
A device used to multiply two analog signals in time domain. Best known for the sound of the Daleks in the original 1960s Doctor Who series. Has some applications outside of music and sound effects. If you can find those old fashioned audio transformers, this effect does not require a power source.
2) Diode clipper: https://en.wikipedia.org/wiki/Clipper_(electronics)
Two diodes in parallel with opposite polarities. Clips the incoming AC signal to a +/- diode threshold voltage. Put a high voltage gain amplifier stage in front of it and you get the classic electric guitar distortion tone you know and love. Allegedly works best with germanium-unobtainium diodes. In their absence, using two different kinds of diodes can also have pleasant tonal qualities.
So many distortion pedals use an op amp to run a signal into antiparallel diodes to create distortion. I’ve spent a few weeks trying to emulate it, and it’s a lot of fun.
Different flavors of diode make significant changes to the way it sounds. Even things like LEDs can be used (they are Light Emitting Diodes, after all).
Andy Simper of Cytomic is some kind of mad genius at this stuff. He’s created a painstakingly accurate emulation of the Ibanez Tube Screamer that allows you to change the values of basically every component in the circuit diagram. It’s jaw dropping: https://cytomic.com/product/scream/
He’s also shared a ton of incredible information about how he emulates circuits. The math can get really intense. If anyone is looking for a fun project, I strongly suggest experimenting with circuit modeling. It’s a great workout for the brain.
As someone also doing audio circuit modeling, Andy is so far ahead of everyone in this game. Have you seen his latest? https://www.kvraudio.com/forum/viewtopic.php?p=9149872#p9149...
> 2) Diode clipper: https://en.wikipedia.org/wiki/Clipper_(electronics)
I don't even know how many Boss DS-1 clones I've made, but the first one was probably when I was in high school about 35 years ago.
> If you can find those old fashioned audio transformers, this effect does not require a power source.
Audio transformers are available both on Aliexpress and Ebay, although I would probably trust more a Triad TY-250P which is about €5 each at Mouser.
Step recovery diode!
Abuse minority carrier lifetime to very suddenly turn from resistive to capacitive just after switching from forward current to reverse bias; use the fact that the current wants to keep flowing to force it to concentrate into another step recovery diode that's about to cut out, in turn making the cut off spike even sharper, and on.
Surprisingly capable for e.g. blasting a FET gate off while tanking the Miller effect gate current needs through sheer power of SRD-based-pulse-shaping. Because for e.g. GaN and SiC if you have to choose between ZVS and ZCS, you can take ZVS and just furnish a gate pulse that _makes_ the channel remain off as the current drops and the voltage soars. At least if you pull some tricks and make the current commutation loop sufficiently low inductance to keep your transistors from blowing out in self-inflicted overvoltage due to a current that needed to pass too high an inductance in too short a time. (Total drain charge is sadly fundamental to the channel's existence, and non-ZVS turn-on is unavoidably lossy. A majority carrier device is theoretically capable of just switching off though if you can arrange the structure for extremely low inductance.)
> 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)
I just had a quick look at the service manual, but isn't that more of a diode bridge than diode ring? A Ring Modulator has the diodes connected nose-to-tail in a ring, but the gain cell in the 33609 looks more like a rectifier :-)
You can see the same circuit in the VCF and (incorrectly drawn) in the VCA of the Korg MS50 synthesizer. In the former it acts as the "variable resistor" in a fairly straightforward Sallen-Key lowpass filter (there are two feedback capacitors, one to either side of the bridge, to attempt to prevent the input voltage also tuning the filter). On the VCA the diodes are drawn wrong but the pin numbers are correct.
Zener diodes can be used as the basis for a quantum random number generator.
https://opg.optica.org/optcon/fulltext.cfm?uri=optcon-1-7-15...
These are also good noise sources and were use in several early video arcade games for producing explosion and spaceship thrust sounds.
https://en.wikipedia.org/wiki/Noise_generator
For log converters you should not use diodes, because their parasitic currents mask the current component that has an exponential dependence from the voltage.
For log converters, bipolar transistors are used, because their collector current depends only on the ideal diode current of the base-emitter diode, not also on its parasitic currents, so the base-emitter voltage has a logarithmic dependence on the collector current, for a relatively wide range of currents.
You could also make a high speed signal sampler.
https://w140.com/tekwiki/wiki/Sampler
Diodes are also used as a radiation detector in radiotherapy: https://oncologymedicalphysics.com/diode-detectors/
And particle accelerators ! They mostly detect gamma radiation, and they are used in conjunction with other detectors (ram chips, mosfets)
From my hobbying decades ago there is also the boring old rectifier to convert AC to a wavy DC.
Those are covered in the article
With some capacitors you can build a voltage multiplicator
https://en.wikipedia.org/wiki/Voltage_multiplier
Yeah, I remember one of these my brother cooked up to power a He-Ne laser tube way back when... It was lots of fun to apply to other off-label experiments too.
4. Voltage controlled filter, (diode ladder VCF), as used in the Roland TB303
Diode ladder, but also in various Sallen-Key designs like the Steiner-Parker Synthacon which we all now know from the Arturia Minibrute (Yves Usson probably made more of these filters than Nyle Steiner ever did!) and as I've mentioned elsewhere the Korg MS50. I think the Yamaha GX1 filters used a diode bridge too, probably using discrete transistors similar to the Korg 700S filter.
PIN diode, a diode used as an AC on/off switch by passing current through it, very useful in RF circuits above 1GHz
I'm always amazed at the circuit hacks that look utterly disgusting until you realize that they're the most practical solution at high frequencies.
Clipping diodes are common in distortion effects as well, especially guitar distortion pedals. Examples include silicon, germanium, LEDs, etc.
I was always partial to the 6AL5 dual diode, which can handle over 300 volts:
https://www.radiomuseum.org/tubes/tube_6al5.html
https://www.r-type.org/pdfs/6al5.pdf
Stereo decoder. You feed L+R and L-R to the corners of Full Bridge Rectifier and out comes Left and Right.
I heard his voice while reading this.
In synthesizers, diodes are used in oscillators to shape triangle waves into sine waves.
Temperature sensor.
I did this once with a diode when I was a baby electrical engineer in college. But of course you need some kind of measurement circuit. So somehow(???) I figured out I could wire a diode into one axis of my analog Gravis joystick--hooked up to my soundcard--and get a fairly accurate and stable measurement of temperature by poking the monostable multivibrator (pretty sure that's what it was called) in the soundcard that would trigger the time it took to drain a set amount of charge through the joystick's x-axis/now-diode.
Novices who don't have a clue nor know any better come up with the weirdest solutions. I have no clue whatsoever now what inspired me to even try something like that.
And you managed to reinvent the single-slope ADC :-)
https://www.cedarlakeinstruments.com/archives/841
https://www.monolithicpower.com/en/learning/mpscholar/analog...
> I have no clue whatsoever now what inspired me to even try something like that.
A combination of "what's the simplest thing that could possibly work?" and "well they didn't say you couldn't..."
Kinda interesting to hear about. I have a 500 chassis I’m slowly working on filling. I’m between the RND 535 or 543, and had never heard of a diode bridge comp before looking at the 535.
What kind of 33609 clone do you have?
I have the Heritage HA-609A. I considered going 500-series. Maybe some day in the future. For now, I have two preamps and the HA-609A in a 4U rack, and most of my other gear is in storage. Keeping things light.
And a square law detector!
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)
Looks great! Would you have a recommendation for intro materials to help me learn the basics of electronics using CircuitLab? I have a working understanding of signal processing but building an actual circuit without electrocuting myself, not setting my Raspberry Pi on fire, or selecting the right set of components for the simplest DIY project based on spec sheets are a mystery to me.
Not sure if it’s a fit for what you’re looking for, but maybe https://ultimateelectronicsbook.com/ (maybe more theoretical than practical).
I’ve heard good things about “Practical Electronics for Inventors” but haven’t gone through it myself.
> Diode Cascade Voltage Multiplier
A favorite of mine and one of the most common ways to generate a pretty high voltage DC. The full wave version pairs well with a center tapped secondary of a resonant transformer.
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-...
In some early computers, the bootstrap was actually a matrix of diodes where you'd remove a diode to get a one and leave it in for a zero. I had a bunch of these boards sometime in the mid 1970's and found you could program a fully populated board with a 9V battery - basically connect it across a diode in a bit position where you wanted a '1', there would be a small but pretty flash from inside the glass case as a zero turned into a one.
When things like the 74S188 were available, we had so much fun squeezing bootstrap code for PDP11's into 2 of them; 32 words by 16 bits was more than enough (later I got code that would boot five different devices into 256 words).
And here's another that's always fascinated me -> Diode Ladder Filter.
https://www.youtube.com/watch?v=jvNNgUl3al0
Diode ladder filters are a mainstay of old analogue synths... and sound awesome.
They certainly do… I’ve few in my Eurorack synth
Btw you can try these out online with a circuit simulator
https://www.falstad.com/circuit/circuitjs.html
The description of forward current and the graph are completely wrong. The graph shows approximately linear current above 600 mV, and the text says "When the threshold is cleared, the diode admits current that’s roughly proportional to the “excess” applied voltage, an ohmic behavior that’s a consequence of the resistance of the material itself".
The current through a diode is exponential with voltage, not "proportional". The graph shows 1.6V applied to a diode yielding 250 mA. In reality, this isn't possible since you'd get a huge current and destroy the diode.
See the Shockley diode equation: https://en.wikipedia.org/wiki/Shockley_diode_equation
I'm surprised that nobody has mentioned that the article is messed up, so am I missing something here?
The Wikipedia equation there mentions the formula ignores the contribution of the internal resistance, which would make it proportional. It seems the article assumes that resistance is a significant contribution (possibly even just from their voltage source) while you assume it is not, for any given particular diode being evaluated or measured, either could be right
Wikipedia says:
> Internal resistance causes "leveling off" of a real diode's I–V curve at high forward bias. The Shockley equation doesn't model this, but adding a resistance in series will.
For small diodes and all LEDs as far as I know, it will level alright. Leaving behind a cute little smoldering crater where the now vaporized diode used to be.
https://www.onsemi.com/download/data-sheet/pdf/1n4001-d.pdf
Take this very generic diode here. When mounted as instructed for the highest heat dissipation, it should gain 50°C per Watt. The flattening of the Current-Voltage curves starts at around 1A. As the diode heats up, the resistance lowers. Extending the limits.
Maximum before damage is 150°C. Minus 25°C ambient leaves us 125°C. Divided by 50°C/W gives us 2.5W. Around 2.8A-3A at 0.8V-0.9V forward voltage.
But the curve is barely proportional at 5A. You might also notice that the datasheet doesn't provide numbers beyond that point. Presumably because the diode left the room then.
In practical diodes it's much more likely to be a minimal contribution.
> The diode is given neither the mathematical rigor of linear circuits nor the red-carpet treatment of the transistor
Sedra/Smith dedicates Part I chapter 4 (pages 174-229 in the 7th edition, not counting the exercises) to diodes. That's longer than chapter 5 (MOSFETs) or chapter 6 (BJTs), and a substantial portion of chapter 3 is devoted to pn junctions. "The Art of Electronics" by Horowitz & Hill dedicates less space to diodes, but it's also much less mathematically rigorous. And they have you building radios & diode mixers before they introduce any sort of transistor. So I'm not sure I agree with this line since neither of the two most popular university electronics textbooks really fits that characterization. It's definitely true of many online electronics "tutorials" though.
Thank you. I was on the fence posting my comment earlier but I’m glad I’m not the only one who is tired of blog posters leading a subject with a blatantly false statement.
I have used some regular diodes today as a way to lower the input voltage and this case is not covered. A diode might be more effective than a buck converter because all I wanted was to have a 0.7V lower voltage and the converter can not work in this condition. Zener diode can but it dissipates too much heat for high-current application.
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.
Lectenna / Rectenna https://en.wikipedia.org/wiki/Rectenna
You can extend the voltage doubler idea to even higher voltages with the voltage multiplier:
https://en.wikipedia.org/wiki/Voltage_multiplier
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.
For low voltage diodes you can use mosfets to get ultra low voltage drop, or just buy dedicated "ideal diode" components that are specifically for that: https://www.analog.com/media/en/technical-documentation/data...
You can also build a rectifier with no voltage drop using an op-amp with some diodes in the feedback loop. But that might be considered cheating :)
at that point (and in general) you'd like to use Schottky ones. MOSFETs are an option for low extra efficiency.
Also the octaver…
https://www.geocities.ws/diygescorp/diodeoctaveup.gif
> ... There is a positive charge on the n-side and a negative charge on the p-side.
How completely unintuitive.
You can blame Benjamin Franklin for that. By the time we figured out the mistake, the standards were set in stone.
It would be like this either way.
The N side has negative charge carriers. It has a positive charge in the depletion region because the charge carriers are missing. Likewise, the P side has positive charge carriers, and when they’re missing, you get a negative charge.
This is true whether we live in the current universe or live in an alternate universe where we say that electrons have positive charge. The depletion region is where the charge carriers are missing (depleted), so you get the opposite charge of whatever the charge carriers are.
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
TL;DW: Isn't that just because the diode matches the PV array's max power point, assuming they both use the same technology (e.g., silicon)?
It seems like that depends on the diode string and PV array remaining at approximately the same temperature as heat is dumped into the diode.
> 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.
In some of my early experiments with little radio transmitters some 30-odd years ago I managed to burn my fingers to an astonishing degree with little plastic transistors like ZTX300s and BC548s.
I remember my late father also commenting around that time "How come a 2N3866 which is rated for a couple of watts can get so hot it melts all its legs off when it's running off a half-flat PP3 battery?", astonished as yet another 2N3866-based amp got a bit lively and melted its legs off despite only running off a half-flat PP3 battery.
So yes I can believe a string of diodes would be a more effective heater than a resistor.
Intriguing, but wouldn't it be even more efficient to just paint something black and let the sun heat it directly?
At the cost of very efficiently radiating that heat back out into space at night.
Making electricity and then using that electricity to heat something elsewhere lets you insulate, effectively allowing you to create a box that heat energy can only pass one way.
We have a one-way diode technology for heat, it's called "glass", and it'll bump your efficiency by about 25% versus uncovered flat plates on a still day. More in windy conditions etc, lots of hand waving assumptions about spherical cows in a vacuum etc.
You'd need some kind of storage for the heat, something with a large thermal mass that doesn't readily give up it's heat to the surroundings. Sand or water or even big rocks or a thick slab of concrete.
depends how hot you want to get something
where is this 'extra' heating coming from?
I suspect (didn't watch) it's just that a diode makes a crude MPPT tracker (since a PV array is just a bunch diodes arranged to collect photons at the P-N junctions). The benchmark is probably "non-variable resistor".
You suspect correctly.
For people who don't know much about solar panels mystified about this:
Solar panels are not ideal voltage sources, their internal impendance varies depending on temperature and the amount of light falling on the panels. Because the point of maximum power in the circuit is achieved when the internal and external impendances are matched, a simple resistive circuit is inefficient and results in the panel converting less light into electricity. If you had a variable resistor, you could adjust it over the day to match the panel, but it is of course easier to use a semiconductor device that does this for you. Any halfway decent battery charger setup or PV inverter has one, but if you are building your own heating system, just stringing together a bunch of diodes might sound stupid, but totally works.
my thought was that a diode removes all the current from its voltage drop (aka: why your LED will burn out if it gets uncontrolled current). A resistor will never remove all the current going through it.
Maybe we're saying the same thing in different ways.
From the misleading sound-bites themselves, they’re know to increase conversation metrics.
This article reads like study notes for the Canadian Advanced ham license exam. It's a great crash course on diodes.
Back in the oldschool days in the 1990s, I remember our school had soldered diodes, that is, we pupils had to do so manually. That was quite fun. Unfortunately I haven't quite had a need or use case to do so again; I tried to get into arduino, but I found it too much needing self-learning. With that I mean I'd have to understand a lot in order to do something useful. I have no problem with learning something new, but my time is super-limited these days and I need to prioritize hard, so I kind of gave up. Perhaps I try for Raspberry Pi but I am afraid it will also require a lot of time investment before it becomes "useful" (aside from learning something new, which is always useful, but other things also need to be learned, so time is of limited value here).
Is (like the article said) this information really not taught in electronics curriculum anymore? It's been a while since I was in school, but this was all covered in my undergrad EE 2XX/3XX classes. Do modern designs use fewer diodes and more ICs in their place?
I’m sure it is still taught, but a lot of power designs do often now swap diodes out for actively controlled mosfets, for example in power multiplexing (there are integrated chips called ‘ideal diodes’ or eFuses which use mosfets that do it all for you), or swapping the diodes in DC/DC converters with mosfets (called ‘synchronous rectification’).
Exciting! I've been out of the field for a while - thank you for what'll be some interesting reading
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.
I know we're on hacker news, but let's just say I misread the title.
And keeping up with the spirit of HN, we would have hopefully learnt something new either way.
Was looking for this comment
I went up 4:30 am today for a flight to Gothenburg, pretty tired and slow... and you and me both.
I had a friend in high school who brought in the Tesla coil he made with among other things a PSU from an old computer.
I pestered that kid so hard about DC-DC voltage regulators and he did not know enough electronics to design one from first principles. I think ladder circuits was as far as he got. But I wanted step-down not step-up transformers.
15 years later when the first gen of really good LED flashlights with built-in voltage regulators popped up I owned at least one at all times.
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.
I've been looking for something to do with the bag of 1N4001 diodes I trash-picked decades ago. There are 1,000 pieces minus the dozen or so I've used in projects. The 50V PIV and slow switching speed limits their application, but I have a lifetime supply!
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..)
> 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?
While diodes alone are not suitable for complex logic, they were instrumental on making computers cheaper in the late vacuum tube era. Vacuum tubes have fairly low reliability and short usable life so having too many of them in your computer is really bad for the cost and reliability of your system. Early transistors were not much better. They would get better over time, but cheap, reliable mass produced diodes were available long before transistors got there.
And while diodes alone cannot do it, a system with a few vacuum tubes to provide the gain and driving a whole lot of diodes made a lot of computers possible at price points that vacuum tubes alone could only dream of. An example is the hacker folklore sweetheart LGP-30, of The Story of Mel fame. 113 vacuum tubes driving 1500 diodes made for a computer that was the size of a fridge, weighed 800 pounds, drew 1.5kW and cost $50k (~500k in modern money), which made it pretty much a personal computer for the late 50's.
They might be referring to RTL (resistor-transistor logic). A transistor in the circuit can maintain the same output current that was input. (A transistor in fact a diode and a half.) RTL was superseded by TTL (transistor-transistor logic) but, hey, the Apollo computers that put astronauts on the Moon used RTL logic.
You could start with the late Don Lancster's book [1].
I have a little "breadboard helper" that I am wrapping up (that includes a project manual) for creating RTL circuits and others [2]. (I hope to sell a few.)
RTL book [1]: https://archive.org/details/RTL_Resistor-Transistor_Logic_Co...
Prototyping [2]: https://cdn.bsky.app/img/feed_fullsize/plain/did:plc:oxjqlam...
https://en.wikipedia.org/wiki/Logic_family has a list of common families; of particular note is CMOS, which is essentially what modern computing is based on.
Bebop To The Boolean Boogie might be useful for you - it's kind of a kids book but the concepts are all well done.
I'll be honest. I misread the title as "Things you can do with dildos"
Wait 'til you hear about vibe coding.
And good for you for saying outloud what many other people also experienced
Not present and ultimately-cursed - using LEDs not only as bridge rectifier but also as the voltage drop for power conditioning before going into a processing IC.
I'm not called the LED Punisher without reason!
Interesting coincidence. I should receive a bunch of diodes from digikey today to fix the bridge rectifier on the control board of our pool heater.
You can also use a bunch in series as a cheap voltage dropper (eg to make a PC fan run slower/quieter).
Nice timing. I just saw pikuma's email with his new course on digital electronics and saw this here.
or.. detecting a nuclear event? https://www.alldatasheet.com/datasheet-pdf/view/124266/MAXWE...
Current/voltage chart looks a lot like a RELU.
That's exactly why it's called a 'rectified' linear unit! It's a half-wave rectifier. The ReLU function is just what you'd see if you put an (ideal) diode on a curve tracer.
(Although to be more accurate, it would be what you'd see on an I-V curve tracer if you measured an ideal diode in series with a 1-ohm resistor. The diode by itself would just go vertical at the Y axis, and the ML people would mutter into their beards about exploding gradients.)
And that diode would be an exploding grenadiant?
Yes, because the slope of current versus voltage goes infinite as soon as the voltage goes positive. The math would explode, and so would the diode, given enough current.
before silicon, rectification was often achieved with copper oxide
forgot adc converter! series diodes tapped at each connection.
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> The diode might be the most neglected component in the electronics curriculum today.
Nonsense like this is why I don’t read lcamtuf. His “electronics 100” falls short of any standard-issue books - today and in the past. And you can open any of them up and very often the very first thing they discuss is the Diode, not only because it’s an “easy” case to begin understanding semiconductor materials (as opposed to tube diodes), but because it forms the basis of understanding more complicated semiconductor devices and why they work the way they work.
I’ve been wholly unimpressed by lcamtuf’s output on this subject because he’s trying to teach but doesn’t know how. He’s trying to come across as smart but his covering of the subject matter is dwarfed by someone like Forrest Mims, which is amusing to think about.
Pick up a book by someone like Melvino or Floyd. They cover analog, digital, computer systems, all sorts of shit. Even the old NEETS books along with technician manuals are a godsend. NEETS approach is particularly good because it moves between phenomena and application in a broad spectrum, which is what helps for concepts to stick.
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I misread the title at first and forwarded this to my wife.