Join the discussion
Write your take first — we'll ask for email only when you're ready to publish.
- Hacker News
- 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.
- at that point (and in general) you'd like to use Schottky ones. MOSFETs are an option for low extra efficiency.by xxs
- 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 :)by tiniuclx
- 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...by jotux
- You can extend the voltage doubler idea to even higher voltages with the voltage multiplier:
- Lectenna / Rectenna https://en.wikipedia.org/wiki/Rectennaby blankx32
- 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.
by brucehoult - 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.by eimrine
- > 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.by uvaursi
- 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?
by kens - 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 rightby manwe150
- Btw you can try these out online with a circuit simulator
- And here's another that's always fascinated me -> Diode Ladder Filter.by djmips
- Diode ladder filters are a mainstay of old analogue synths... and sound awesome.by iainctduncan
- 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-...by sehugg
- 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).
by zh3 - 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)
by compumike - > 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.
by MisterTea - 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.by dr_kiszonka
- 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.
by dietrichepp - Diodes are also used as a radiation detector in radiotherapy: https://oncologymedicalphysics.com/diode-detectors/by joconne
- You could also make a high speed signal sampler.by summa_tech
- 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.
by adrian_b - 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...
by bob1029 - > 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.
- 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.)
by namibj - 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.
by exDM69 - 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!
by nomel