hybridfree/eevblog-posts huggingface dataset:
Diode Clipping - Page 1
Forum section: electronics / beginners

author: Legion
author_rank: Frequent Contributor
timestamp: March 21, 2014, 09:54:42 pm
content: I built these circuits:The top circuit works as expected, dropping about 0.8V in each direction and clipping the rest of the top and bottom of the signal. This is as measured at the indicated test point and ground tied to terminal B of the FG.I tried many variations of the second circuit. Resistors on the A side of the FG, resistors on the B side (as shown in the schematic), resistors on the anode side of each diode, resistors on the cathode side, etc.My expectation was that the resistors would drop more of the voltage in addition to the 0.8V in each direction, in effect clipping less of the signal. Instead the entire signal comes through unaffected once the resistors are added. Why is that?

author: Simon123
author_rank: Regular Contributor
timestamp: March 21, 2014, 10:08:34 pm
content: Try adding resistor after signal generator .

author: ConKbot
author_rank: Super Contributor
timestamp: March 21, 2014, 10:12:45 pm
content: Add some series resistance to your source. Current your voltage source is ideal, zero source impedance. If there was a source impedance then it would behave as you expect. Once the diodes turn on, the source impedance and 100 ohm resistors make a divider, so it no longer clips, but instead reduces amplitude once it exceeds the threshold. In audio equipment terms, its a signal compressor.http://www.mediacollege.com/audio/processing/compression/However your compression ratio will vary with the source impedance.If you had tried this on a bread board, with a beefy AC source, then you would have let some magic smoke out of some diodes. Just for giggles, in your simulation, see what the currents in the diodes are in the first case.

author: Legion
author_rank: Frequent Contributor
timestamp: March 21, 2014, 10:24:27 pm
content: Quote from: ConKbot on March 21, 2014, 10:12:45 pmThere is source impedance. It's an FG with 50R output impedance.

author: josip.budimir
author_rank: Newbie
timestamp: March 21, 2014, 10:37:36 pm
content: The diode always wants to keep the required voltage for itselfSo if you have a 1V supply, the diode will measure 0,7V and the resistor 0,35V would make the resistor measure 4,3V and the diode 0,7To measure current in a circuit with a diode in series, you have to take out the 0,7V drop voltage from the input voltage in the formula I=U/RLets say your supply is 0,8V the resistor is 10ohm's and a diode in series the current is:I=(U-0,7)/RI=0,1/10I=0,01ASo if you have a supply under 0,7V, youre gonna get very low or no current
Diode current in a rectifier circuit - Page 1
Forum section: electronics / beginners

author: Meshka7
author_rank: Contributor
timestamp: February 28, 2015, 07:48:16 pm
content: So I'm going through this book and reading about diodes. There are these elaborate equations to calculate the ripple and avg/max current in the diode. In one example, the max current is calculated to be 2.5A. The author concluded that the diode has to be spec'ed for at least 2.5A.So I simulated circuit, and while LTSpice shows the max current to be only 1.6A, the initial charging current goes all the way to 8.2A. So if I'm using a 2.5A diode, I am out of luck and my rectifier diode will get destroyed by the surge.Here is the circuit:https://www.dropbox.com/s/gppvgw7d2ywru9g/Full%20Wave%20Bridge%20Rectifier.asc?dl=0However I looked up the 1N4001 datasheet and found 2 paramters : Average rectified output current (1A), and peak forward surge current (30A). The first parameter is a little mysterious. Average with respect to what? (given that the diode is on only for a short amount of time). So is it average while the diode is on? That would correspond to the calculated average from the book which is half the max which would be 1.25A (the book derive that iDmax = 2 * iDavg) and we would be out of spec with the 1N4001 (1.25A > 1A).The 8.2A would be within the surge max 30A parameter and all is good, but that renders the calculated max of 2.5A useless. Is there a rule of thumb to calculate the max surge current out of the max repetitive charging current?

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: February 28, 2015, 08:16:15 pm
content: Quote from: Meshka7 on February 28, 2015, 07:48:16 pmThey mean that you must take theintegralover 1 period.

author: Meshka7
author_rank: Contributor
timestamp: February 28, 2015, 08:23:09 pm
content: The one period average in the same example was calculated to be 66mA. I guess this makes it way within spec. But again, how would I have figured out that the real max is 8.2A??

author: dannyf
author_rank: Super Contributor
timestamp: February 28, 2015, 08:35:45 pm
content: QuoteThe instantaneous current can be extremely high, especially if you have a large capacitance bank with low ESR.However, most rectifiers are very hardy - they can take repeated peaks 100 - 200x of their average ratings no problem (schottky diodes are not as hardy).Also, do a FFT on the current and factor in the winding capacitance in the transformer, etc. It is one of those simple circuits that can get very complex quickly.

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: February 28, 2015, 08:40:41 pm
content: Quote from: Meshka7 on February 28, 2015, 08:23:09 pmThats is not so easy. You have to know al the internal resistances, the moment in the sinewave that power is turned on, and the exact characteristic of the diode. Knowing al that you end up with afirst or second order differential equation, that needs solved.If solved, you get a function for the current in time. To find the peak, you take thederivativeand solve it to zero.

author: Meshka7
author_rank: Contributor
timestamp: February 28, 2015, 09:57:15 pm
content: Thanks All.
diode esd damage - Page 1
Forum section: electronics / beginners

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: January 18, 2019, 04:45:06 am
content: can diodes like axial 1n4xxx, 1n4148 or zeners be damaged by typical esd?

author: Zero999
author_rank: Super Contributor
timestamp: January 18, 2019, 01:33:45 pm
content: Yes, it should be fine.Of course everything has it's limits. Even humans can be badly damaged by ESD: a bolt of lightning can kill!The most sensitive part, as far as ESD is concerned is the MOSFET. Most other parts are fairly robust.Distributors such as Digikey and Mouser put almost everything in ESD safe bags and containers so it's safe to put them near more sensitive components and it's cheaper to just keep one stock of packaging material, rather than ESD safe and non-ESD safe types.

author: Ian.M
author_rank: Super Contributor
timestamp: January 18, 2019, 01:48:19 pm
content: Laser diodes, many RF diodes and some LEDs are ESD sensitive. As others have said, regular silicon diodes are not very ESD sensitive. It all depends on junction area and materials and whether or not reverse breakdown is likely to cause hot-spotting before the rest of the junction can avalanche or Zener. MOSFETs are ESD sensitive because of insulation breakdown of the very thin gate oxide layer.
Diode frequency - Page 1
Forum section: electronics / beginners

author: yalect
author_rank: Regular Contributor
timestamp: April 22, 2020, 12:58:14 pm
content: Hi,I would like to ask you about transit frequency of some diodes.- Can I find diode transit high frequences above 100Mhz, what (schottky diode) like for exampleBAT41a highest frequency could transit?- at highest frequencies the diode could pass or transit a half side of signal or negative side ontrary to what we are used to.- may you provide me a picture or graph shows and explain the signal at highest frequency?Thank you

author: Etesla
author_rank: Regular Contributor
timestamp: April 23, 2020, 05:10:22 pm
content: The main parameter of the diode that matters here is reverse recovery time. If the reverse recovery time is too long, the diode won't work well as a diode at higher frequencies. In your case, at 100 Mhz, you would desire a reverse recovery time around (a tenth of half the period) = 1/(100*10^6)*1/2*1/10 = .5 nS, which is crazy fast. Only a handful of diodes in the world can pull that off. For comparison, the BAT41 diode you mentioned has a reverse recovery time around 5 nS, which is still pretty fast.However, the reverse recovery time is not the only thing that matters. The circuit around the diode and the way it is being used also matters a lot. Generally, the harder you use the diode (more current through it), the faster it will act. Depending on how you use the diode in your circuit, a BAT41 might work, or it might not...The attached PDF just demonstrates the things using a random diode I already had the model for, that BAT54, which is similar to the BAT41. As you can see, at 10 Khz, it worked as expected. At 100 Mhz, with a 'light' load (not a lot of current through it), it didn't work at all. At 100 Mhz with a 'heavier' load, it kind of worked as expected.So the main takeaways are:Finding a diode with a reverse recovery time that is on par with the speeds you want to use it at is importantThe way the diode is used has a huge impact on how it will act, especially at higher frequencies
Diode identification help - Page 1
Forum section: electronics / beginners

author: quicknick
author_rank: Contributor
timestamp: April 16, 2023, 11:30:33 pm
content: Hello,Can anyone point me in the right direction regarding this diode?: (pic 1)The rings seem to be red-red-'something' (first red band is the cathode), where 'something' looks either greenish or bluish depending on the light...It is removed from a vintage video card that I'm repairing (Asus GeForce 2 GTS), where it failed in a half-shorted state, leading to the burning of R22 from the schematic below (pasted here from the US3007 datasheet). Problem is that the datasheet doesn't mention anything about such a diode (I've added it in redto correspond with the implementation on the Asus board): (pic 2)The board works just fine after removing the diode and replacing the burnt resistor, and the Nvidia reference implementation doesn't use the diode and also does away with the 10 ohm resistor, but one has to wonder, did Asus install the diode for no reason? (pic 3)

author: Kim Christensen
author_rank: Super Contributor
timestamp: April 16, 2023, 11:39:51 pm
content: Maybe it's a 14V Zener diode? Red Red Green?See attached datasheet:

author: quicknick
author_rank: Contributor
timestamp: April 18, 2023, 10:26:23 pm
content: Thank you, that must be it! I'm ordering a few...

author: ppTRN
author_rank: Regular Contributor
timestamp: April 19, 2023, 10:52:45 am
content: The US3007, in the pin description section, says for the V12 pin (pin 28):This pin is connected to the 12 V supply and serves as the power Vcc pin for the outputdrivers. A high frequency capacitor (typically 1 uF) must be placed close to this pin andPGND pin and be connected directly from this pin to the GND plane for the noise freeoperation.Since the pin is already connected to 12V I am betting that the diode is a zener for over voltages protection, that's why it works fine widout it
diode in a crossover design - Page 1
Forum section: electronics / beginners

author: SnakeBite
author_rank: Regular Contributor
timestamp: January 29, 2014, 10:57:02 pm
content: Hello,i designing 2nd order crossover and i was wondering , why i never saw reverse bias diode placed across the inductors to protect from "inductive spikes" when you turn off the amplifier?Idop.s. the inductors i use are 0.51mH each

author: David_AVD
author_rank: Super Contributor
timestamp: January 29, 2014, 11:46:28 pm
content: I assume you're talking about a passive crossover ?It's an AC circuit so why would there be a inductive spike anyway?Adding a diode across the inductor would just shunt it on half of the audio waveform.
Diode in series with BJT Base - Page 1
Forum section: electronics / beginners

author: TaylorD93
author_rank: Regular Contributor
timestamp: March 09, 2022, 02:51:17 am
content: Hi All,Ive been looking at an old article for a 10A PSU where it uses multiple LM317's, but i noticed in its control/regulation circuit something i have seen in other Linear PSU's from the 70's/80's and im not sure why its there.In this schematic, what is the purpose of D1? Is it to force the 741 into essentially equivalent to an open collector output? i.e. to only allow for sinking of current, and preventing the opamp from reverse biasing the BE junction of T1? If for example T1 had a reverse VBE voltage rating of 6V, the 741 could exceed this depending on its supply voltage and cause Vbe of T1 to break down?If it is to only sink the current, why wouldnt something like an LM311 be used instead?thanksTaylor

author: fourfathom
author_rank: Super Contributor
timestamp: March 09, 2022, 03:04:12 am
content: A quick guess: The 741 wasn't a rail-to-rail opamp, so the directly-connected output would not be able to swing high enough to shut off that transistor. Adding the series diode does the trick.

author: magic
author_rank: Super Contributor
timestamp: March 09, 2022, 08:39:08 am
content: Reverse breakdown can only occur if A can pull the emitter several volts lower than B (and sinks all the resulting R2 current).LM311 wouldn't work because comparators aren't stable in negative feedback circuits.

author: SeanB
author_rank: Super Contributor
timestamp: March 09, 2022, 08:51:12 am
content: July August 1990 Elektor, and yes the diode is used because a 741 will pull up to 3 diode drops below the positive rail (2v typically) when saturated, and here you need to be able to control the output of the 741 to within a little more than 1V2 below the output, as the LM317's provide the 1V2 output voltage difference, while the 741 will only be up to 1V8 of the supply rail. Thus the extra diode, so the transistor can actually be fully cut off to raise the output voltage.Not great powering the 741 from the output, if you moved the supply to the input instead you would increase control voltage range, to allow your output to be better controlled at the lower end, as the IC would still have full internal bias, but you are still limited by the ability of the 741 to pull the output down to 0V, and thus still have 4V as lower bound. Separate the 741 and drive, to say a -5V rail from a separate power supply and regulator, possible here as you only need 20mA or so of current flow, and you could pull the output all the way to 0V. Feed this into point D, move R5 lower end to the 0V rail of the output at point O, along with the meter negative and the negative end of C4. Then power pin 7 of the 741 from point G and you will have a better power supply.
Diode knee voltage. - Page 1
Forum section: electronics / beginners

author: Jimbz
author_rank: Contributor
timestamp: March 26, 2015, 01:18:28 am
content: Hello everybody, small question:What is a diode knee voltage ? And what is diode forward drop ?As far as I figure, the knee voltage is the minimum voltage required for the diode to allow conducting the smallest bit of current ?And forward voltage drop is the value to fully make the depletion zone disappear ?

author: IanB
author_rank: Super Contributor
timestamp: March 26, 2015, 01:22:55 am
content: How about this?https://www.google.com/search?q=diode+knee+voltage&tbm=isch

author: Dave
author_rank: Super Contributor
timestamp: March 26, 2015, 03:29:47 am
content: Quote from: Jimbz on March 26, 2015, 01:18:28 amNope. Diodes conduct anywhere above 0 volts (and below for that matter). It's just that the function of current with respect to voltage is exponential, so the current below the knee voltage will be very small.

author: TimFox
author_rank: Super Contributor
timestamp: March 26, 2015, 12:30:40 pm
content: As the previous poster stated, diodes conduct at all voltages. The I vs. V curve goes continuously through the origin (0,0) with a finite slope.In the forward bias direction, the current increases exponentially (very fast) with voltage, so there is no well-defined "knee".In the reverse bias direction, as the voltage goes negative the negative current saturates at a low "leakage" level, but increases abruptly at a well-defined knee voltage, becoming a Zener diode.For on-purpose "Zener" diodes with knees greater than about 5 V, the diodes are actually "avalanche" diodes and the current increases much faster above the knee than with true Zener diodes at, say, 3.3 V knee.By the way, if you are measuring current for a diode in a glass case (e.g., 1N4148), you may see current at zero voltage due to photocurrent induced by room lighting.
diode latch - Page 1
Forum section: electronics / beginners

author: wiresaho
author_rank: Contributor
timestamp: May 29, 2024, 12:12:59 pm
content: Is it possible to make a latch with diodes - I saw this ->Or is it including transistors with it to get the memory bits?

author: Psi
author_rank: Super Contributor
timestamp: May 29, 2024, 12:20:18 pm
content: You can make gates out of just diodes, but there is no amplification, no small current able to drive larger current.So I believe they still use transistors as buffers/inverters. Otherwise you can't series diode-based gates together without absurd current requirements from each additional gate adding more draw through the gates before it.

author: ledtester
author_rank: Super Contributor
timestamp: May 29, 2024, 12:23:25 pm
content: A full writeup of the Diode Clock, design files and LTspice simulation files may be found here:https://hackaday.io/project/11677-the-diode-clock#:~:text=DDL%20Devices,grab%20files%20here%3A(scroll down to "DDL Devices")Here is the datasheet of the hex NOR board:https://cdn.hackaday.io/files/11677499588768/DDL01_datasheet.pdfand here is the schematic of a NOR gate from the datasheet:Read the datasheet for a detailed desciption of how it works. Note that V_RF is an AC source operating in the MHz range.

author: wiresaho
author_rank: Contributor
timestamp: May 29, 2024, 01:56:48 pm
content: If it didn't have inductors in it, it would probably work hydraulicly and pneumaticly as well.But they do have pneumatic "transistors" as well.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 29, 2024, 04:50:16 pm
content: lolll wow but consumes almost 5 amps ... current hungry for sure

author: David Hess
author_rank: Super Contributor
timestamp: May 30, 2024, 12:01:38 am
content: Quote from: Psi on May 29, 2024, 12:20:18 pmNegative resistance devices can be used in place of amplification, like tunnel diodes, DIACs, or 4 layer diodes. Neon bulbs can also be used.

author: Psi
author_rank: Super Contributor
timestamp: May 30, 2024, 08:59:24 am
content: Quote from: David Hess on May 30, 2024, 12:01:38 amInteresting.
Diode marking SJ79A - Page 1
Forum section: electronics / beginners

author: Venti
author_rank: Newbie
timestamp: December 14, 2024, 01:47:39 am
content: Hello friendsAfter spending the evening on trying to find anything about this diode or a suitable replacement i am trying to ask here.In an older device (2009) there are these diodes in a bridge rectifier. Their marking is SJ79A. Based on logo search it should have been produced by General Semiconductor. Thank you in advance.

author: fzabkar
author_rank: Super Contributor
timestamp: December 14, 2024, 05:49:18 am
content: The logo belongs to Vishay (General Semiconductor). One possibility is S07J rectifier diode (600V).https://www.vishay.com/docs/85733/s07b.pdfhttp://markingcodes.com/search/c/sjThe photo appears to show 4 diodes in a bridge rectifier configuration.

author: Venti
author_rank: Newbie
timestamp: December 16, 2024, 11:08:40 am
content: fzabkar thank you very much.
Diode Marking - Page 1
Forum section: electronics / beginners

author: Rick Law
author_rank: Super Contributor
timestamp: February 24, 2014, 01:51:09 am
content: I have seen diode and rectifiers with three different markings on the negative side:1. A solid (usually silver) color line all around the diode at the negative end2. A broken (or should I say dotted?) line around the diode at the negative end3. A pair of broken lines lines around the diode at the negative endThese different markings must mean something. Searching for "diode marking" just isn't helping me finding the answer...Help appreciatedRick

author: w2aew
author_rank: Super Contributor
timestamp: February 24, 2014, 03:07:58 am
content: Quote from: Rick Law on February 24, 2014, 01:51:09 amTo my knowledge, no, they all mean one thing ... "this is the cathode"

author: pickle9000
author_rank: Super Contributor
timestamp: February 24, 2014, 03:40:09 am
content: A tvs is double banded isn't it? I'm an old guy excuse me if I'm wrong.
Diode not conducting - Page 1
Forum section: electronics / beginners

author: Ciji
author_rank: Newbie
timestamp: July 14, 2025, 07:04:56 am
content: I'm trying to simulate a basic half-wave rectifier circuit in Ansys Electronics Desktop 2024 R2 (Nexxim Transient) using the built-in Level 6 diode model.For validation, I ran the same circuit in LTspice and it works correctly. I see expected rectification. However, in Ansys Circuit Designer, the simulation completes without errors, the input waveform is correct, But the output voltage is always flat (0 V). I get this warning: Only one connection for node net_3. The diode doesnt seem to conduct. Does anyone know what could be wrong with the connection or the model? . I have attached related images in following order: a) circuit schematic, b) simulation waveform c) Diode model parameters

author: bostonman
author_rank: Super Contributor
timestamp: July 14, 2025, 01:26:36 pm
content: Am I reading your frequency correctly, you're running it at approximately 2GHz?The diode is probably a piece of wire at that point. Not sure why it works in Spice, but try decreasing your frequency to 100Hz or so.

author: mikerj
author_rank: Super Contributor
timestamp: July 15, 2025, 09:35:42 am
content: What are the specifications of the diode e.g. junction capacitance, reverse recovery time?

author: jwet
author_rank: Frequent Contributor
timestamp: July 16, 2025, 06:08:33 pm
content: The model looks really thin. There are really no AC parameters much less microwave type parameters. It looks like a pretty standard diode with a .8v drop.Spice or ANSYS doesn't care what the frequency is if the model has no AC parameters...it might as well be DCWhat value is RL? Is it defined somewhere? If RL was zero, you could get what you're seeing.Look at currents, its obvious that IR across RL is zero, so either RL is zero or I is zero.Which node is node 3, run that down. It could be as simple as a drafting error where two things are connected (overlapped?)

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 16, 2025, 09:09:54 pm
content: Apart from the 2.5GHz issue...Quote from: Ciji on July 14, 2025, 07:04:56 amMaybe it's a quirck of the importer / converter program. If you can't identifynode net_3easily, then just delete all the wires and redraw them.
Diode On TV Power Supply  - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: May 05, 2013, 04:12:14 pm
content: Hey guys just wanted to know im looking at a 19" LCD tv which when connected to the mains will only stay in stand by mode so straight away whipped off the back and had a little look tested all the capacitors and they are fine and when it came to testing the diodes one of them is allowing a flow either way would that be enough to prevent the tv from turning on even for a split second???

author: SeanB
author_rank: Super Contributor
timestamp: May 05, 2013, 04:40:21 pm
content: Could be a faulty diode or a faulty capacitor across it. Unsolder the diode and check it out of circuit, then do the same for the little 470pF capacitor as well. Norcal715 on Youtube had a video about this recently.

author: Unknown
author_rank: Unknown
timestamp: May 05, 2013, 05:00:08 pm
content: Brilliant thankyou
diode or diode connected FET? - Page 1
Forum section: electronics / beginners

author: sempjam
author_rank: Newbie
timestamp: November 09, 2015, 02:13:09 pm
content: I'm trying to get to grips with when you would want to use a diode connected FET instead of just a diode.In my particular example I'm thinking about an rf dc rectifier (diode + low pass filter). In many cases I see people using a MOSFET with shorted gate/drain instead of a Schottky or other high frequency diode.I'm wondering if anyone knows what are the advantages of one configuration over the other?Thanks!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 09, 2015, 03:07:21 pm
content: Something like a PN4117 is sometimes used as a low leakage clamp. Tie D+S together and use G to (D+S) as a diode, A-K. This has rather high internal resistance, ca. 5kohms, so it makes a poor diode, but that doesn't matter much for something like an electrometer.The recovery won't be any better than usual, because it's minority carrier conduction. Normally you don't forward-bias the gate. I'd expect the RF performance is worse than using the JFET properly (which works on fast majority carriers).MOSFETs can be "diode strapped" (gate to drain), but this is only useful for generating a characteristic voltage (e.g., in CMOS current mirrors). The body diode (source to drain) remains. In monolithic circuits, the substrate is a separate connection, so this is okay, but four-terminal discrete MOSFETs are essentially hen's-teeth nowadays.For RF rectification, schottky diodes are preferred. They're fast (majority carriers, without having to worry about gates and amplifier bias!), and leakage isn't much of a problem.Tim

author: sempjam
author_rank: Newbie
timestamp: November 10, 2015, 09:48:25 am
content: Thanks Tim! Much appreciated
Diode Placement for RF (Signal Tracer) - Page 1
Forum section: electronics / beginners

author: AngraMelo
author_rank: Regular Contributor
timestamp: September 21, 2021, 04:00:42 pm
content: Hello everyone,Ive built myself a little signal tracer, it is nothing more than an audio amplifier with a probe. I also built a 1kHz oscillator for injecting signal if needed. Many people when building such devices also use a Germanium diode for RF detection.The thing is that the diode most of the time is used in parallel with the probe as displayed in the picture. This configuration makes no sense to me.Could anyone please explain to me why is the diode in parallel?

author: bob91343
author_rank: Super Contributor
timestamp: September 21, 2021, 05:08:41 pm
content: It's just a rectifier. One of many possible circuits. The input capacitor gets charged on the half cycle and then on the other half cycle its voltage is added to the input, a sort of voltage doubler. At that time, the diode is reversed biased.

author: TimFox
author_rank: Super Contributor
timestamp: September 21, 2021, 08:12:38 pm
content: This configuration of the diode rectifier is used when the input capacitor (10 nF) blocks any DC from the probe tip, rectifying the AC component only.In the other configuration, where the probe tip connects directly to the diode, the rectification depends on the DC level at the tip.
Diode purpose - Page 1
Forum section: electronics / beginners

author: lumdef
author_rank: Contributor
timestamp: March 15, 2025, 09:01:47 am
content: What is the purpose of this single 1N4148 diode? Can current flow from the emitter to the collector in that case?

author: benj38
author_rank: Frequent Contributor
timestamp: March 15, 2025, 11:10:55 am
content: The text says it all: "when the voltage on the base of the first transistor sees 0.6V + 0.6V+ 0.6V = 1.8V..."The first 0.6V above is the VBE of the left-most transistor, the second 0.6V is the VBE of the right-most transistor, and the third 0.6V is the voltage drop on thediode.Why should there be a problem for the current to flow between the emitter and collector of the right-most transistor? If one were to reverse the diode such that its cathode was connected to the collector, then you would have a problem.

author: RoGeorge
author_rank: Super Contributor
timestamp: March 15, 2025, 11:10:59 am
content: The diode shifts up or down, all at once, the detected voltages in the "staircase".If you insert zero, one or more diodes where the D1 is, the input voltage to turn on the first LED will change accordingly (and it will change with the same amount for the following LEDs, too). The "distance" between each voltage step in the "staircase" remains the same, but the beginning voltage of the entire "staircase" moves.

author: awesomechapro
author_rank: Contributor
timestamp: March 15, 2025, 11:17:07 am
content: In very simple terms, think of it as being there to increase the "thresholds" of the transistors. This ensures that LED 1 needs a little more voltage to turn on, preventing it from activating at a very low voltage.

author: David Hess
author_rank: Super Contributor
timestamp: March 15, 2025, 11:18:46 am
content: The diode raises the threshold of the first transistor by 0.6 volts to 1.2 volts. This is often done to increase noise immunity.

author: lumdef
author_rank: Contributor
timestamp: March 15, 2025, 01:13:58 pm
content: Thank you, it is clear now.
Diode question... SR206 bad or good? - Page 1
Forum section: electronics / beginners

author: Doc38343
author_rank: Contributor
timestamp: June 26, 2015, 07:49:09 pm
content: I am trying to trouble shoot a board and was checking the diodes and came to this one that the reading is not as I think it should be.It is an SR206 A11 (black w/silver band)In google it pulls up a data sheet for a schottky.....I get a .198 reading using the Fluke 87V....I am getting a .4 range on all the other diodes on the board but I was not sure on a Schottky if it is expected to show similar good range as the other types.I pulled it out of circuit to test because it is beside a coil and reads both ways when in circuit.if I reverse polarity it holds the OL reading as it should...Any help appreciated... I looked at the datasheet but am still too green to decipher more than the obvious(I don't have a replacement but I don't want to put a bad part back in either)Thanks a mill....

author: w2aew
author_rank: Super Contributor
timestamp: June 26, 2015, 08:09:39 pm
content: Schottky diodes generally have about half the forward voltage of ordinary silicon PN diodes, so all things being equal, it looks OK.

author: Doc38343
author_rank: Contributor
timestamp: June 26, 2015, 08:18:47 pm
content: Thanks and I had finally found the same conclusion on G search....... I was sorta hoping that was the trouble so back to the scratch and sniff hunt
Diode replacement options?  - Page 1
Forum section: electronics / beginners

author: peps1
author_rank: Regular Contributor
timestamp: May 14, 2021, 10:52:00 pm
content: Hello, I'm trying to fit an inductive sensor onto a 3D printer and the instructions call for a BAT85 to stop the 24v powering the sensor being sent to the 5v mainboard, unfortunately, I don't have one to hand.I was wondering if I could substitute for something I have to hand:1n40011n40021n40041n4148Bzx55c4v7 ZenerBzx55c5v1 Zener

author: ataradov
author_rank: Super Contributor
timestamp: May 14, 2021, 11:23:50 pm
content: 1n4148 should work fine here. Its Vf is still under 1 V under all currents and temperatures. And for room temperature and low current it is about 0.5 V.

author: peps1
author_rank: Regular Contributor
timestamp: May 14, 2021, 11:43:27 pm
content: thank you, Alex!
Diode replacement - Page 1
Forum section: electronics / beginners

author: Daxxin
author_rank: Regular Contributor
timestamp: December 25, 2016, 09:41:01 am
content: need to replace 1N4937 at moment i only have BYV26E wathing datashet seems to be similar ...its ok ?

author: David Hess
author_rank: Super Contributor
timestamp: December 25, 2016, 01:43:09 pm
content: The 1N4937 is a 600V 1A 200ns fast recovery rectifier. The BYV26E is a 1000V 1A 75ns ultra-fast recovery rectifier.The BYV26E is not really a substitute for the 1N4937 because of its significantly larger forward voltage drop however that will not matter in a high voltage circuit which is the only reason to use a 600V 1N4937 instead of a lower voltage alternative.

author: Daxxin
author_rank: Regular Contributor
timestamp: December 26, 2016, 06:30:44 am
content: thanks its working , very low voltage 18v hf trafo output i guess there no big difference no idea why they using that hv diode in the originalcircuit maybe huge stock.

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2016, 07:07:15 am
content: Price wise there is no difference in the low voltage or high voltage variant, and often the high voltage version is a lot cheaper because of volume and because the process control is tight enough that all test out to pass.Your 1N4001 and 1N4007 can come from the same die, and have the same breakdown voltage as well, simply because the majority were marked as 1N4007 as they tested out that way, while they had an order for a few hundred 1N4001 that were simply branded that way, as the diodes tested out to break down at more than 100V. More expensive, simply from the small run.Silicon diodes are a very low cost item for the common types, so making them all to the same spec for a range and simply doing a relabel is cheaper, as you only have to do a single test cycle, and any that fail are scrapped and sold unlabelled and unmarked. Those diodes are then bought as scrap, and used after some basic sorting, by the cheapest manufacturers to make the cheap knockoffs, as they want to cut cost, and test all incoming as they know they will get fakes and recycled components.

author: David Hess
author_rank: Super Contributor
timestamp: December 26, 2016, 07:14:39 am
content: They might have used it just to limit the number of separate parts kept in stock. I do the same thing; why keep all of the different 1N4933 series of diodes, 50 to 600 volts, when the 1N4937, 600 volts, can almost always be used in place of all of them?The BYV26E is really intended for a different set of applications like high voltage high efficiency switching power supplies but in many cases like Sigmund Freud said, a diode is just a diode.
diode string or smps? - Page 1
Forum section: electronics / beginners

author: questOn
author_rank: Newbie
timestamp: January 15, 2013, 02:55:16 am
content: I was tearing apart device with 3,6,9Vdc outputs all powered from a sealed 12V battery..I thought Id find a couple linear regulators( or something more complicated) but to my surprise it was just a string of 12 diodes.. tapped every 4 diodes ( guessing forward bias is about 0.7~0.75V ) so each tap gives a three volt drop..clever but Is it? How does this compare to having, say a couple of buck switch modes each configured to give a separate output? I would guess that the voltage out would be more constant with a smps (as well as the load current) as the input voltage varies (battery drains).

author: mariush
author_rank: Super Contributor
timestamp: January 15, 2013, 03:48:54 am
content: It's not very clever because the output voltage will not only vary a bit and power is wasted in the diodes, depending on the current (how much the thing you connect to it pulls).The diodes will get hot and their voltage drop will change with the heat increase (usually) and you're just wasting power in the diodes when you have a battery with limited power available.Linear regulators pretty much would work the same, but they're provide much smoother output, but they'll still waste the volts difference as heat. No efficiency increase (if you output 9v out of 12v, your efficiency is basically 75% while for 3v it would be just 25%), just more stable output voltage.Buck regulators (switching controllers) would be better, and with a smart selection you could get as much as 85-90% efficiency, but they require more components such as an inductor, a schottky diode, 2-3 capacitors and resistors.

author: digsys
author_rank: Unknown
timestamp: January 15, 2013, 04:37:38 am
content: Usually they do that for PRICE ! 12 diodes cost about $1.00 (in small bulk), ANYTHING clever is a few $s, plus you now need a PCB.Many items can handle a small Voltage variation, so in those cases there's NO need for anything fancy. And by fancy, I mean anLM317, 6 resistors and 2 caps + PCB.
diode switch matrix - Page 1
Forum section: electronics / beginners

author: maxwellhun
author_rank: Newbie
timestamp: March 30, 2013, 07:27:30 pm
content: Hi!I made an Mjoy modulehttp://www.mictronics.de/projects/avr-usb-joystick/and in this project we have adiode switch matrix. I would like to control these imputs by microcontroller but I am not sure what is the simplest way to do it. Can I use FET or I should use analog switch IC ?
Diode test and forward voltage drop - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: June 10, 2019, 02:37:09 am
content: I am trying to identify this led. It comes from a laser printer.I did a diode test and 1.43 v is the approx forward voltage drop.Does that mean the meter is supplying 1.43 volts as part of the test?I could see no light coming from the led and the camera showed nothing as well, so I think it may be an infrared led.http://tinypic.com/view.php?pic=29w0bwi&s=9When i use my phone to make a movie of my tv remote, it shows a purplish light blinking.The circuit that contains the "IR" led, has some 178 resistors and two 34 ohm resistors in series that go to the IR led.

author: MosherIV
author_rank: Super Contributor
timestamp: June 10, 2019, 06:44:29 am
content: Yes, the dmm supplied 1.43V (and more) but the Voltage drop across the diode is 1.43VDO NOT LOOK at the laser diode. Yes the laser diode will be in the infra red and not visible.The laser diode will burn out your retina and you will not see or feel anything.

author: fixit7
author_rank: Regular Contributor
timestamp: June 10, 2019, 02:30:07 pm
content: Ok.I wonder what it was used for?It had some kind of lens over it.

author: golden_labels
author_rank: Super Contributor
timestamp: June 10, 2019, 03:05:01 pm
content: While I fully agree with MosherIV — you should never look at a laser diode to see if it works(1)— that doesn’t look like a laser diode.It seems to be a normal LED with collimating lens on top of it. The board itself is sold as “power distribution board”, so I expect it is either an indicator or the emitter part of a detector (e.g. of the case being open). Seeing the other side of the board would help.Also, please consider adding attachments directly to your posts, instead of using 3rd party services.____(1) You can see laser only twice in your life. Once with your left and once with your right eye.

author: Vtile
author_rank: Super Contributor
timestamp: June 11, 2019, 10:01:19 pm
content: Quote from: fixit7 on June 10, 2019, 02:37:09 amActually a bit falsely stated above, the meter is not delivering the voltage/tension for the diode in this type of test. It is rather delivering constant current for the device and measures the tension/voltage generated across the diode. The voltage/tension over measured diode is limited by the sourcing capacity of the meter, but constant current is the input for test and tension/voltage is the response.

author: rfengg
author_rank: Regular Contributor
timestamp: June 12, 2019, 12:29:52 am
content: Most Fluke and other multimeters source a test current of 1mA in the diode mode check.So the voltage you read on the DMM is the voltage subtended across the diode at a test current of 1mA.

author: ogden
author_rank: Super Contributor
timestamp: June 12, 2019, 12:47:42 am
content: Quote from: fixit7 on June 10, 2019, 02:30:07 pmCould be light source part of paper (position) sensor.
Diode testing in circuit best methods - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: April 14, 2020, 11:41:50 am
content: Trying to track down a suspected leaky diode on a matrix of about 40 diodes.Each of them test well on a plain diode test (0.4-0.5 ohms forwards, nothing backwards) but i only have a tiny Fluke 101 so i can't really get a good sense for if the diode goes "bump"Should i grab a cheap analog meter or should i try something else, including a multimeter with quicker / more accurate measurement?

author: Manul
author_rank: Super Contributor
timestamp: April 14, 2020, 01:10:52 pm
content: Can you post a reference schematic, how are these diodes connected? Does not need to be all 40.

author: pwlps
author_rank: Frequent Contributor
timestamp: April 14, 2020, 02:08:43 pm
content: Quote from: Mp3 on April 14, 2020, 11:41:50 amIn principle you should measure the forward voltage threshold, not the resistance. Fluke 101 has a diode test function doing precisely this so I think it should be enough.https://www.circuitbread.com/ee-faq/the-forward-voltages-of-different-leds

author: David Hess
author_rank: Super Contributor
timestamp: April 14, 2020, 05:21:16 pm
content: After doing forward voltage drop tests, I would probably put a low voltage current limited source in series with an ammeter sensitive enough to measure the required leakage. The voltage is adjusted to be as high as the circuit will allow.

author: SeanB
author_rank: Super Contributor
timestamp: April 14, 2020, 05:51:51 pm
content: Use a higher reverse voltage, probably as high as you can generate, within the diode reverse voltage limit, with a current limiting resistor to limit short circuit current on your meter if the diode is shorted, or you connect it the wrong way round. Resistor to limit current on 20mA range to around 15-18mA, and then look to see reverse leakage. It will show up the reverse leaking diode quite well. Pretty much going to be that most small signal diodes, and most sub 3A diodes, will show at most 1mA of leakage current, and as you suspect one of multiple, simple to search to find the ones that leak the most, and replace them.

author: Mp3
author_rank: Frequent Contributor
timestamp: April 15, 2020, 07:30:06 am
content: Quote from: SeanB on April 14, 2020, 05:51:51 pmGreat, i'll try to find a schematic of the board i'm working on and attempt this once i've been sure it's safe to feed higher voltage thru it.
Diode types for receiver - Page 1
Forum section: electronics / beginners

author: mazragors
author_rank: Newbie
timestamp: September 22, 2025, 06:54:25 am
content: Hello EveryoneI want to ask what type and rating of diode would be best suited in such radio receiver circuits - here is the diagram I highlighted the diode with a dothttps://pcbhub.org/anonymous/f2ed5aa3d8e547029dda69e5b24d2370?t=21f4gs4i.e. there are a lot of different ones but it is not marked on the diagram

author: Andy Chee
author_rank: Super Contributor
timestamp: September 22, 2025, 07:00:25 am
content: The diagram shows a crystal set radio.The best diode would be germanium diode, 1N34A, OA91 are a couple examples. The problem is germanium diodes can be difficult to obtain these days.A modern option is a schottky diode, 1N5711, which is more widely available.You can certainly try a conventional silicon diode 1N4148, 1N914 but the signal will be weaker.Don't forget the headphone/earphone should preferably be a high impedance set, piezo earpieces work the best. The standard 16-32 ohm ear pieces used for your mobile phone or MP3 player will not work well.

author: Analog Kid
author_rank: Super Contributor
timestamp: September 22, 2025, 07:59:11 am
content: 1N34A? Easy peasy; my favorite electronic supplier, Jameco,has 'em. $2.95 each.Dunno where you'd find them in Yurp, though. Must be someone who sells them there.

author: Gyro
author_rank: Super Contributor
timestamp: September 22, 2025, 09:18:24 am
content: If you are in Ukraine as your country flag indicates, you should have ready access to former USSR warehouse stocks. From a brief search on ebay, good candidates for point contact Germanium diodes are:Д9Б (D9B)Д18 (D18)Д19 (D19)Д9Л (D9l)... in fact the whole Д9 series should work.These are just a few from a brief search, I'm sure there are many others available locally too.(Looking further, you probably have access to the best selection of cheaply available germanium diodes in the world, including some exotic 150MHz ones, if you want to experiment for best performance).
Diode voltage drop and noise - Page 1
Forum section: electronics / beginners

author: fonograph
author_rank: Frequent Contributor
timestamp: June 04, 2017, 02:23:07 am
content: Does the amount of voltage drop in diode affects how much noise it adds to the signal? Does more voltage drop means more noise?What type of diode have lowest noise,shotky? PIN ? Tunnel diode ? Gun diode?

author: Kleinstein
author_rank: Super Contributor
timestamp: June 04, 2017, 08:35:03 am
content: Usually the voltage drop on a diode is considered relative low noise. For the white noise part the differential resistance is relevant parameter. For the ideal diode this is kT/e / I - and thus independent of the diode. Real diodes usually have a slightly higher resistance. So already at 1 mA the resistance is in the 50 Ohms range and thus a white noise level of only 1 nV/Sqrt(Hz) is expected. In the high frequency region, so that the diode is considered slow, the differential resistance is even lower - thus slow PIN diodes can be even lower noise above some 100 kHz.There might be some additional 1/f or similar low frequency noise contribution. Just from my feeling and picture of how a diode works this is expected to be higher in diodes that are slow and have a higher forward voltage / low leakage. Not much of this is expected for fast gold doped diodes like the 1N4148.Current noise, for the reverse leakage is a different thing. Here charge quatisation gives a major noise contribution, thus again diode type independent - it only depend on the leakage current.

author: danadak
author_rank: Super Contributor
timestamp: June 04, 2017, 12:42:20 pm
content: These might help -http://qucs.sourceforge.net/tech/node68.html#SECTION001123000000000000000http://rfic.eecs.berkeley.edu/~niknejad/ee142_fa05lects/pdf/lect11.pdfhttp://www.ece.ucsb.edu/Faculty/rodwell/Classes/graduate_noise_class/noise_notes_set7_new.pdfpages 21,22Regards, Dana.
Diode with X and 48 marking - Page 1
Forum section: electronics / beginners

author: vinovino
author_rank: Contributor
timestamp: February 01, 2024, 06:04:55 am
content: Can anyone know what type of diode have a marking of X and 48?Please see attached photos of actual diode

author: golden_labels
author_rank: Super Contributor
timestamp: February 01, 2024, 06:35:28 am
content: You didn’t attach any photos. A guess: BAS21W. They follow X4_ markings, with the last symbol indicating manufacturer-specific production facility code.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 01, 2024, 07:04:50 am
content: See if you find it here:https://smd.yooneed.one/

author: golden_labels
author_rank: Super Contributor
timestamp: February 02, 2024, 02:07:35 am
content: Where the diode comes from? What is the device? Photos of its surroundings?Properly identifying SMD components without context is close to impossible.

author: Jwillis
author_rank: Super Contributor
timestamp: February 02, 2024, 02:54:24 am
content: Agreed. The dimensions can also narrow down the exact package being used. Right down to the pitch of the pins. Is it a SOT323, SOT23 or SC59 ?
Diode ? - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: September 12, 2020, 11:49:29 pm
content: Can I use the following pictured diode from Mousser to replace all 3 types.1) 1S19422) 10D103) V06B

author: floobydust
author_rank: Super Contributor
timestamp: September 13, 2020, 12:06:53 am
content: OP, question is relevant to this threadhttps://www.eevblog.com/forum/beginners/diodes-question/msg3214518/#msg3214518just ask it there and delete this one instead of starting another thread

author: tkamiya
author_rank: Super Contributor
timestamp: October 03, 2020, 07:35:02 pm
content: 10D10 is 1000 volt 1 amp. Very commonly used in Japanese design.