I don't have a high frequency LCR and can only test at 100KHz. I tested the 1N4148WS I bought on Taobao (sister site of Aliexpress) which is in the SOD323 package and has 'T4' mark on it and result was measured to be about 0.63pF.
I did another test, even the 1N4148 in DO-35 glass axial package has a junction capacitance of less than 1pF.
Similar result to what we've measured, thanks for taking the time to verify this.
BTW interesting LCR meter, does it support DC bias?
Best,
Its built-in bias voltage is limited to 2.5V, luckily the bid I won included an external
±42V ±40V bias adapter (ZM2328).
Well capacitance has already told that it's not a standard 1N4148.
What/which standard exactly, is it disagreeing with ?
Ideally, be very specific, and include links (free) to it. A Wiki, although very useful and nice. Is NOT really a reliable source (as already mentioned, by another poster), when there are disagreements like this.
I will counter, with a counter example, against what you have been saying. I hope you respect Vishay Semiconductors, as a counter source. Here is a copy, of one of their datasheets, for a 1N4148 diode:
https://www.farnell.com/datasheets/2613993.pdfI can't find any mention of it being conformant to a JEDEC 1N4148 standard. But what it does say, is as follows:
Electrically equivalent diodes:
1N4148 - 1N914
There are all sorts of standards, that have been created over the years, decades and even centuries. But, just because such a standard exists, doesn't mean that it is necessarily used/recognized in modern times. Some standards, seem to have just disappeared from living memory.
E.g. There was an original RS232 standard, complete with standardized 25 pin connector (which may NOT have been aprt of the standard). Over the years, some of the pins got dropped, through lack of use (as modems eventually mostly disappeared from common use), its voltage requirements became more relaxed (lower), and 9 pin varieties, became the 'standard'.
The so called "2N3055" 'standard' Power Transistor, differs for partly complicated reasons, from the now ancient (possibly 1968), original version/specifications. Due to manufacturing practicalities.
That very Vishay reference shown below in a screen capture clearly states diode capacitance 4pf MAX! This is what just about every reference to a 1N4148 shows, regardless of package, some of the surface mount types even have a maximum capacitance of 2pF.
If you have another source for a reference other than Wiki, please provide.
Remember this 1N4148 is referred to as a "Small Signal Fast Switching Diode", not a "General Purpose Rectifier" like the 1N4001, and thus junction capacitance IS important in it's intended usage, although it has become the general purpose small signal diode of use by many, myself included.
Anyway the 1N4148 is like a diode analogy of a M3 bolt, if I go to any hardware store and buy (or order from anywhere) a M3 bolt I expect the threads to be the correct diameter and pitch, the heads and length may be different for different types, but the threads better be correct. That's what I expect and same goes for the universal 1N4148, and 9pF capacitance isn't a 1N4148 in my book, of course YMMV.
Best,
Op is most likely referring to JESD282.
That defines some key parameters under a part number. capacitance is not part of the key parameters.
Reverse voltage , forward current and thermal range are standard. sub classification can add some other parameters. The standard specifies all testing conditions for each of the parameters.
The standard is publicly available and free. Register at jedec.org ( you can even use a gmail address ) and you can grab anything.
Anyway the 1N4148 is like a diode analogy of a M3 bolt ...
Maybe not the best analogy, it doesn't specify the bolt material.
That very Vishay reference shown below in a screen capture clearly states diode capacitance 4pf MAX! This is what just about every reference to a 1N4148 shows, regardless of package, some of the surface mount types even have a maximum capacitance of 2pF.
If you have another source for a reference other than Wiki, please provide.
Remember this 1N4148 is referred to as a "Small Signal Fast Switching Diode", not a "General Purpose Rectifier" like the 1N4001, and thus junction capacitance IS important in it's intended usage, although it has become the general purpose small signal diode of use by many, myself included.
Anyway the 1N4148 is like a diode analogy of a M3 bolt, if I go to any hardware store and buy (or order from anywhere) a M3 bolt I expect the threads to be the correct diameter and pitch, the heads and length may be different for different types, but the threads better be correct. That's what I expect and same goes for the universal 1N4148, and 9pF capacitance isn't a 1N4148 in my book, of course YMMV.
Best,
I agree with you. I've looked further into the (what I suspect the device datasheet of what you actually bought, was), and it breaks too many of the 'standard' 1N4148 diodes characteristics. Even if, those characteristics, are NOT part of the JEDEC speficiation (mentioned in other posts, in this thread, i.e. here:
https://www.eevblog.com/forum/projects/incorrect-labeled-1n4148-diode/msg4168855/#msg4168855 ).
You have convinced me, because of what you said about it being a "Small Signal Fast Switching Diode".
The M3 bolt analogy, has issues. Because, some aspects of an M3 Bolt, may or may not be, part of its 'official' specification.
E.g. Precise weight, specific materials used in its construction, bolt/nut full tighten, release, life expectancy, precise colour, etc. May NOT be part of the specification.
The situation is still complicated, as the devices that you bought, (presumably) meet its available datasheet specification. But I agree, they are not standard 1N4148 diodes, even if no direct link to such a document, has yet been posted (but there is a link to where you can get the documents, via free email registration, so I can register later, and look for myself).
The inferior 1N4148's manufacturer, seem to have decided to make the 4pF maximum, a 5pF typical value, measured at 1.5V rather than 0V. What is also surprising, is that the same manufacturer, seems to sell plenty of very fast, low capacitance diodes, although they seem to be more expensive than the 1N4148's. So, I don't really understand why they didn't stick to the 1N4148's (somewhat or fully) standard definition.
Maybe there is some technical explanation, such as they are really some other part numbered diodes. Which is, they fail the test(s) for what they are suppose to be e.g. higher voltage, low leakage etc. Are then reclassified/sold as 1N4148's, if possible, to ensure they can sell the highest possible number of salvageable (working) dies.
Op is most likely referring to JESD282.
That defines some key parameters under a part number. capacitance is not part of the key parameters.
Reverse voltage , forward current and thermal range are standard. sub classification can add some other parameters. The standard specifies all testing conditions for each of the parameters.
The standard is publicly available and free. Register at jedec.org ( you can even use a gmail address ) and you can grab anything.
Thanks, it is not your fault. But the completely crazy website, keeps on refusing me permission to register, because I can't fathom out, their ridiculous captcha nonsense thing. So, I've given up, after perhaps 10 failed attempts.
The answer you entered for the CAPTCHA was not correct.
I don't get on well with CAPTCHA systems. Basically, see below:
You have convinced me, because of what you said about it being a "Small Signal Fast Switching Diode".
Actual I didn't create that, this is directly from Wiki's description, Vishay's description, Diodes description, Microsemi and others.
The M3 bolt analogy, has issues. Because, some aspects of an M3 Bolt, may or may not be, part of its 'official' specification.
E.g. Precise weight, specific materials used in its construction, bolt/nut full tighten, release, life expectancy, precise colour, etc. May NOT be part of the specification.
Probably not the best analogy, but I would expect the threads to match.
Best,
Probably not the best analogy, but I would expect the threads to match.
They do match, but you are nitpicking about one bolt having unified thread, the other sharp-V. They are both the same pitch , depth and slope , just that one is a bit rounded at the top. They will both fit the same nut. So the chinese versions have a bit of rounding because they use a more relaxed quality control..
If the junction capacitance is so important : buy from a known good source. For 99% of the people this is not a critical factor.
You expect the best quality manufactured under the tightest of QA , then go off and buy chinesium parts from the cheapest vendor out there .
One of my pet peeves is selling "1N" or "2N" devices that have different packages from the original JEDEC registration, without changing the prefix.
For example, plastic or SMD re-package of a 2N2222, which is a TO-18 metal package through-hole device. Of course, there are legitimate "PN2222" and similar part numbers for plastic-package equivalent devices.
On the other "thread", note that the modern American "Unified National" thread form is defined identically to the modern ISO metric thread form in terms of geometry.
https://www.boltscience.com/pages/screw6.htm
My understanding, is that there are two different ways, a 1N4148 could be designed into a circuit. I'm showing two extremes.
One is, that it is basically what some/Dave(EEVblog) likes to call Jelly Bean parts, such as the 1N4148. E.g. A 1N4148, being pulled to the 5V rail, via a 1K resistor, with almost 5mA flowing through it. I.e. The circuit is nowhere near any datasheet limits, and a simple jelly bean part, fits the bill just fine. That is where you could use your cheapest, worst manufacturer, riskiest supplier(s) for. Depending on how you value the quality of your final product(s).
Alternatively, it is a critical part of a circuit, really accurately, dependably and reliably needs to respond within 2.000 nanoseconds, for every pulse. In a circuit which really needs the reverse recovery time, diode capacitance and other circuit parameters, to be within certain specified limits. In which case, I'd suggest considering a specific, very high speed diode, characterized for such uses, with suitable design margin, for best quality/dependability and reliability.
Which, if it is decided to stick with a 1N4148, should then be a specific manufacturers's part (number), with a suitably good quality pedigree, behind that manufacturer.
It is exciting, using powerful test equipment, to measure tricky things. Either because the test equipment originally cost $20,000, 15 years ago, and it allows amazingly accurate and detailed tests to be performed. Or to design your own test equipment, that measures complicated parameters, with your own, home brew modifications.
But, to use either of the above equipment, to measure, what probably arguably is a generic jelly bean part, in some fairly rare, partly obscure way. Then complain, because (what seems to be), the cheapest possible supplier, from the cheapest possible component of that type they sell, then disregarding their claimed datasheet values. Then making a panic, panic, panic, a jelly bean part differs from a specification, because they measured it at 1MHz/1.5V, and gave a typical value (on the datasheet), of 4 or 5pF, rather than at 1MHz/0V, and had a maximum value of 4pF, is perhaps a little bit of an over-reaction. Sorry, if this causes offense.
As I see it, the critical part, is that it DID agree with their published datasheet, if I've followed this thread, correctly. Therefore is arguably, at least a little bit unfair, to create a complaint thread, without clearly stating that fact, right from the start.
My basic understanding, is that jelly bean parts, are NOT 100% bolted down, in overall specifications, across ALL manufacturers and available parts. They are what was easily and very cheaply being made available, at that time. E.g. 741 op-amp or 555 timer. Yes, they do have somewhat basic specifications, bolted down. But if you get into the fine detail and/or need certain parts of its specification, to be EXACTLY what you desire. You need to choose an exact/specific 741 (partly obsolete these days) or 555 timer, from a specific manufacturer. Then carefully go over their datasheet and perhaps discuss the situation with the supplying company, if your purchase volumes and/or contacts in the industry, permit.
TL;DR
No datasheet violation = Arguably no big problem, as the (specific/actual) datasheet should really be consulted, if certain parts of the component specification, really matter, in the actual use case.
There are standards, but my understanding is, that those should NOT be relied upon, too much. I.e. Datasheets should be used and/or consulting with the actual supplier(s) and their application engineers.
That very Vishay reference shown below in a screen capture clearly states diode capacitance 4pf MAX! This is what just about every reference to a 1N4148 shows, regardless of package, some of the surface mount types even have a maximum capacitance of 2pF.
So its not really standardized among the major manufacturers. Some are 1.5, 2, 4pF max.
I get the frustration, but this is not so different from buying a 2pF 1N4148 and then getting pissed when you buy another and a 4pF diode shows up.
edit, I did manage to find one on digikey, diotec semi 4pF typical
https://diotec.com/request/datasheet/1n4148.pdf
Alternatively, it is a critical part of a circuit, really accurately, dependably and reliably needs to respond within 2.000 nanoseconds, for every pulse. In a circuit which really needs the reverse recovery time, diode capacitance and other circuit parameters, to be within certain specified limits. In which case, I'd suggest considering a specific, very high speed diode, characterized for such uses, with suitable design margin, for best quality/dependability and reliability.
Which, if it is decided to stick with a 1N4148, should then be a specific manufacturers's part (number), with a suitably good quality pedigree, behind that manufacturer.
If a standard 1N4148 diode (read less than 4pF and 4ns) does the job then no need for a specific very high speed diode, here's exactly where the 9~10pF and 8ns "jelly bean diode" might cause a problem tho!!
It is exciting, using powerful test equipment, to measure tricky things. Either because the test equipment originally cost $20,000, 15 years ago, and it allows amazingly accurate and detailed tests to be performed. Or to design your own test equipment, that measures complicated parameters, with your own, home brew modifications.
Nothing tricky about measuring diode capacitance, nor requiring $20K equipment, it's relatively simple and straight forward if you understand the solid state characteristics of PN junctions and the synchronous techniques to make such measurements
But, to use either of the above equipment, to measure, what probably arguably is a generic jelly bean part, in some fairly rare, partly obscure way.
As stated and referenced earlier the 1N4148 is a "Small Signal Fast Switching Diode", note the "Fast Switching" terminology, which directly implies things such as recovery time and capacitance are important, certainly not "fairly rare" nor "obscure" as you stated, since after all it is a Fast Switching Diode not a general purpose rectifier
Then complain, because (what seems to be), the cheapest possible supplier, from the cheapest possible component of that type they sell, then disregarding their claimed datasheet values. Then making a panic, panic, panic, a jelly bean part differs from a specification, because they measured it at 1MHz/1.5V, and gave a typical value (on the datasheet), of 4 or 5pF, rather than at 1MHz/0V, and had a maximum value of 4pF, is perhaps a little bit of an over-reaction. Sorry, if this causes offense.
Almost all 1N4148 sources show the maximum reverse recovery time a 4ns (Vishay, Semitech, Diodes, Rohm, On Semi, MCC, and others), Wiki lists this directly in the 1N4148 specifications, yet the diode in question, the 1N4148W from Jingdao Micro shows a 8ns maximum recovery time and also shows a graph of capacitance of over 10pF at 0.1V bias, while others sources mentioned show an absolute maximum C of 4pF at zero volts and 4ns maximum recovery!!
Anyway, there is no panic, nor overreaction from knowledgeable folks, they know what a 1N4148 diode should be, and a 9~10pF with a 8ns recovery time diode is
NOT a 1N4148 in my book, and frankly that's all that matters here at the Labs!!
Best,
If a standard 1N4148 diode (read less than 4pF and 4ns)
Yet you cannot point us to this "standard".
Please do share with us the source (beyond your personal belief) of what 1N4148 actually specifies.
If a standard 1N4148 diode (read less than 4pF and 4ns)
Yet you cannot point us to this "standard".
Please do share with us the source (beyond your personal belief) of what 1N4148 actually specifies.
What we consider a loose "standard" and you may differ, but if the vast majority of all sources show a 1N4148 with less than 4pF and under 4ns reverse recovery and only one (maybe a few others) shows 9~10pF and 8ns, I'll side the majority
Of course this isn't a "proper" standard, but does have some backing as a tried and true 1N4148 dating back 50 years ago and we've used them since then
Even a "Jelly Bean Diode" using JEDEC nomenclature 1N4148 shouldn't justify typical capacitance spread of over 14 to 1. I don't believe the usual "Jelly Bean Parts", such as 1N4004, 1N5817, 2N3904, 2N2222, 2N3906, and so on show this kind of important parameter variation, if you know of some please enlighten us!!
BTW the 1N4148 cap ratio of over 14 to 1 points to a completely different 1N4148 core die design. This is not a process variation, but a completely different die design, probably with a completely different diffusion profile, and hints that maybe a substitute die is being used!!
Best,
Think we've wasted enough of our and others time and BW on this subject. If you chose to view the 1N4148 as a generic jelly bean diode without much regard to capacitance and reverse recovery parameters, go ahead and do so
We chose to call this particular Jingdao Micro 1N4148W a rogue 1N4148 and will sent them to the junk pile or trash can!!
Anyway, our original intent was to alert folks to this excessive capacitance in the Jingdao labeled 1N4148W diode, not create a pi&&!ng contest
BTW if anyone wants these Jingdao 1N4148W diodes, just send a SASE and we will happily provide them!!
Best
BTW the 1N4148 cap ratio of over 14 to 1 points to a completely different 1N4148 core die design. This is not a process variation, but a completely different die design, probably with a completely different diffusion profile, and hints that maybe a substitute die is being used!!
Different manufacturer puts different thing inside "equivalent part", only you seem shocked/outraged by this. There is not a designated 1N4148 design/die/factory/process, its just a designation for some common set of specifications, which are in a standard, but you want to "own" instead.
Stop using "standard" for your position and this false authority, there is already an authority which publishes the standard you are ignoring and refusing to acknowledge.
Feel free to sign up and extract the standard if you are so wedded to designing by the designation 1N4148, and do share with us what it actually contains. Another poster says it does not specify capacitance. Likely it doesnt but you continue to promote your ideal that is does/should (without evidence).
Part dies change often enough that designing to off spec parameters (as you are doing) leads to problems. Instead of acknowledging this and accepting you didnt check (ever?) the standards and specifications, you make out like its the manufacturers fault for not achieving your
ideal imaginary
"standard".
We chose to call this particular Jingdao Micro 1N4148W a rogue 1N4148 and will sent them to the junk pile or trash can!!
And I'll keep pointing out that its your unsubstantiated opinion on that matter, sure seems like a 1N4148.
for the nth time : Capacitance is NOT part of a jedec classification unless you drill into the suffixes.
a 1N number , without any trailing digits specifies 4 parameters.
For rectifier diodes, the Type Administrator will insist that a new type number, not a suffix letter, be used, if a
new device differs from an older registered device in any of the following respects:
1) Any change in forward current rating, except surge current.
2) Any change in reverse voltage rating.
3) Any change in maximum storage or operating temperature rating.
4) A new rating or characteristic not required of the older device and for which industry agreement for
reregistration of the older device could not be reached.
5) A major change exceeding the greatest change permitted for suffix designations in one or more of the
characteristics listed.
6) New outline dimensions.
Capacitance is not in that list.
There is this clause too:
Commercial data describing that device must identify by asterisks all parameters which appear on the JEDEC registration.
For example this datasheet :
https://www.onsemi.com/pdf/datasheet/1n4001-d.pdf explicitly calls out the JEDEC parameters. Vrrm , Vrsm , Vr , Io , IFSM.
To get a new JEDEC number your part needs to be substantially different from any existing part BEFORE they will create a new classification. so, if a part is close enough to an existing part you don't get a new number.
For parts that have letter suffixes (1N4148A 1N4148R etc)
The letter R means it is a reverse polarity , the letter M is a case deviation. other letters are new types.
The suffix denotes a tightening of an original specification. you can replace a 1N4148 with a 1N4148W , but not the other way around.
To get a letter suffix there are also rules.
Forward Voltage (VFM) 0.8 - 0.9 x VFM (reg)*
Reverse Current (IRM) 0.05 - 0.20 x IRM (reg)*
Surge (Nonrepetitive) Peak Forward Current (IFSM) 1.50 - 3.50 x IFSM (reg)*
Reverse Recovery Time (trr) 0.10 - 0.50 x trr (reg)*
So a 1N4148x can have 1/10 of the original recovery time.
There are also so called "Slash sheets" 1n4148/696 would be equivalent to an automotive qualified part AEC-Q101
The slash sheet defines a number of parameters that are brought under control. The original 1N4148 does not conform to any of those. These are additional "tightening" parameters ( And accoupling testing methods. JEDEC specifies the testing method. you can't just do whatever, that would be meaningless for comparison)
Many manufacturers violate JEDEC by not clearly marking the controlled parameters or by creating part numbers that violate JEDEC nomenclature. 1N4148-DO35 would be such a violation. It needs to be a single letter, a dash and number sequence or slash and number sequence. Anything else is junk
In short, if you would have bought a 1N4148-xyz and it does not meet capacitance specs you could complain. but 1N4148 is not "tight" enough of a specification to include the capacitance. You'd have to check RDF22 to see what nomenclature includes that. unfortunately i can;t help, i don't have access to those anymore. I left the whole semiconductor stuff 8 years ago
Different manufacturer puts different thing inside "equivalent part", only you seem shocked/outraged by this. There is not a designated 1N4148 design/die/factory/process, its just a designation for some common set of specifications, which are in a standard, but you want to "own" instead.
No joke, of course it's a different die design, how else could it have 14X capacitance difference!! I'll wager that under noopy's microscope the Jingdao 1N4148 die looks completely different than the other 1N4148 die from Vishay, On Semi, Diodes, and so on. Likely there aren't many semi fab houses producing 1N4148 wafers for obvious $ reasons, and most sources are using these few fabs for wafers and packaging in different formats and also likely exchanging packaged parts. Would not be surprised to find that the Jingdao die is from another part type, not even intended for the 1N4148 diode.
Where do you get off thinking I'm shocked for outraged, or what do I "own"?? And how is a 14 to 1 capacitance "equivalent"?? As for specifications, did you happen to notice a parameter called reverse recovery time, it's a specification and listed even in the early 1N4148 predecessor called the 1N914 (see original TI data sheet from 1960). The Jingdao is specified as a max of 8ns whereas everyone else is specified as a max of 4ns. Maybe this is "equivalent" to you, as is the capacitance??
Stop using "standard" for your position and this false authority, there is already an authority which publishes the standard you are ignoring and refusing to acknowledge.
I'll use standard all I want, it's an acceptable level as I stated for what I expect a 1N41418 to be, what authority are you??
Care to show your standard as you mentioned? If it's JEDEC, this requires a fee.
Part dies change often enough that designing to off spec parameters (as you are doing) leads to problems. Instead of acknowledging this and accepting you didnt check (ever?) the standards and specifications, you make out like its the manufacturers fault for not achieving your ideal imaginary "standard".
Never stated we designed anything around this diode. As stated earlier, if you bothered to read, this was purchased long ago as a general stock item with quite a bit of other items from LCSC, likely a couple years back. Only reason we discovered this was while measuring zener diode capacitance and did a few other diodes, we found this excessive capacitance. The Jingdao is a rogue 1N4148 in our book, and that's all that matters here!!
And I'll keep pointing out that its your unsubstantiated opinion on that matter, sure seems like a 1N4148.
Can you justify the 8ns reverse recovery (goes along with the higher capacitance), vs the 1N4148 specification of 4ns (see image)??
The Jingdao might seem like a 1N4148 to you, but not here
BTW note the TI 1N916 (1N4148 predecessor) data sheet from 1960, they use milli-microseconds for nanoseconds and uuF for pF!!
Best,
for the nth time : Capacitance is NOT part of a jedec classification unless you drill into the suffixes.
a 1N number , without any trailing digits specifies 4 parameters.
...
Forward Voltage (VFM) 0.8 - 0.9 x VFM (reg)*
Reverse Current (IRM) 0.05 - 0.20 x IRM (reg)*
Surge (Nonrepetitive) Peak Forward Current (IFSM) 1.50 - 3.50 x IFSM (reg)*
Reverse Recovery Time (trr) 0.10 - 0.50 x trr (reg)*
...
So a 1N4148x can have 1/10 of the original recovery time.
However, the reverse recovery time is a specification as you've shown, and the Jingdao 1N4148W has a specification of 8ns maximum, and the max specification from Wiki for a 1N4148 is shown as 4ns which jives with all the other 1N4148 sources mentioned except Jingdao! Since a larger junction capacitance implies a longer recovery time this makes sense.
So again we consider the Jingdao 1N4148 a rogue 1N4148 and the higher reverse recovery time supports this
Edit: You noted: "
The suffix denotes a tightening of an original specification. you can replace a 1N4148 with a 1N4148W , but not the other way around." This won't apply with the Jingdao 1N4148W because the Jingdao is well outside the 1N4148 reverse recovery specification as shown and thus would fail in many applications.
So the Jingdao 1N4148W should not be considered a 1N4148W as it fails the 1N4148 replacement.
Best,
The Jingdao is a rogue 1N4148 in our book, and that's all that matters here!!
Actually, it's NOT all that matters here!!
Thanks, you've just given me evidence, that it is indeed 1N4148 compatible**.
**Because I'm reasonably happy with the original 1N914's performance, as a high speed diode, instead of a 1N4148. The datasheet(s) you seem to supply, would seem to show, that the 1N914 was originally specified as 3.5ns TYPICAL reverse recovery time. Which in my book, can mean around 7 or 8ns, is a suitable estimate as a maximum value, in very rough, back of envelope, non-committed, terms.
TL;DR
I have rather liked the 1N914's (long story). So, illustrating that this 'rogue' 1N4148 has similar reverse recovery times to it, has made my day!
From just above your post, within
quotes from free_electron that we posted just before your post.
Edit: You noted: "The suffix denotes a tightening of an original specification. you can replace a 1N4148 with a 1N4148W , but not the other way around." This won't apply with the Jingdao 1N4148W because the Jingdao is well outside the 1N4148 reverse recovery specification as shown and thus would fail in many applications.
So the Jingdao 1N4148W should not be considered a 1N4148W as it fails the 1N4148 replacement.The original 1960 data sheet for the 1N914 and 1N916 from TI preceded the introduction of the 1N4148 which was introduced in 1968 according to Wiki. The present 1N4148 specs are listed in Wiki and reverse recovery is listed as 4ns maximum which jives with various sources. Since reverse recovery and junction capacitance are tightly related, with the measured non-Jingdao 1N4148W capacitance that we and others measured, one would expect lower reverse recovery times than 4ns.
We measured a SMD 1N4148W that had a 0.657pF zero bias capacitance, this low capacitance was confirmed by another. With this low a zero bias junction capacitance the reverse recovery should be very quick indeed, maybe under 2ns
BTW, "
here" refers to our Labs here, not on this site!! Obviously everyone's opinion matters on this site, although some seem to be questionable
Best,
Capacitance is NOT part of the RDF for a base JEDEC number. And please stop using wikipedia. nobody designs using Wikipedia "specs"
You also cannot refer to 1N914 datasheets. The reason there is a 1N914 or 1N916 is that they are deemed sufficiently different to merit their own classification. you cannot shove a 1n4148 under a 1n914. They have different numbers again because they are sufficiently different.
The 1N4148W can be used as a 1N4148. neither capacitance nor recovery time are part of the original 1N4148 base number.
The real question would be if the jingdao 1N4148W meet other 1N4148W specs. You need to compare fuji apples to fuji appels. not mix boscop or honeycrisp with fuji. they are all apples. but they have distinctive subclassification.
As for measuring the capacitance : that needs to be done with a test frequency of 1MHz ... i don't think your LCR bridge goes that high. You need a semiconductor parameter analyzer for that.
Capacitance is NOT part of the RDF for a base JEDEC number. And please stop using wikipedia. nobody designs using Wikipedia "specs"
You also cannot refer to 1N914 datasheets. The reason there is a 1N914 or 1N916 is that they are deemed sufficiently different to merit their own classification. you cannot shove a 1n4148 under a 1n914. They have different numbers again because they are sufficiently different.
Sorry, but don't have a JEDEC or another spec source, care to provide one? Otherwise I'll keep using Wiki and various known manufactures such as On Semi, Vishay, Diodes, and so on. The 1960 TI reference was to show how far back this type of High Speed Switching Diode dates, not to use it as a reference even tho it does show capacitance curves and indicates Reverse Recovery Times. So this was referred to as the 1N4148 predecessor which showed up in 1968, but not to be compared with.
The 1N4148W can be used as a 1N4148. neither capacitance nor recovery time are part of the original 1N4148 base number.
Interesting, since this is directly from one of your above posts,
quoted directly below? Seems to indicate Reverse Recovery Time as a parameter, along with the usual other diode parameters. Please clarify what part of your posts should we accept and what part should we reject?
The suffix denotes a tightening of an original specification. you can replace a 1N4148 with a 1N4148W , but not the other way around.
To get a letter suffix there are also rules.
Quote
Forward Voltage (VFM) 0.8 - 0.9 x VFM (reg)*
Reverse Current (IRM) 0.05 - 0.20 x IRM (reg)*
Surge (Nonrepetitive) Peak Forward Current (IFSM) 1.50 - 3.50 x IFSM (reg)*
Reverse Recovery Time (trr) 0.10 - 0.50 x trr (reg)*
So a 1N4148x can have 1/10 of the original recovery time.
The real question would be if the jingdao 1N4148W meet other 1N4148W specs. You need to compare fuji apples to fuji appels. not mix boscop or honeycrisp with fuji. they are all apples. but they have distinctive subclassification.
Well we've compared apples to apples and according to other 1N4148W specs (Vishay, Diodes, Semtech, MCC, On Semi, and so on) the answer is the Jingdao 1N4148W does not match or even approach the capacitance and reverse recovery (maybe more parameters, but we didn't check) specs!! Exactly why IMO this should not be considered a 1N4148W.
As for measuring the capacitance : that needs to be done with a test frequency of 1MHz ... i don't think your LCR bridge goes that high. You need a semiconductor parameter analyzer for that.
Yep, that's what the diode data sheets show and all our diode capacitance measurements were at 1MHz, and the LCR meter used was the Hioki IM3536 which supports up to 8MHz. We designed and built a special test fixture structure to support DC Bias measurements for this purpose (details posted on another thread), since the IM3536 only supports internal +-2.5VDC bias. We use either a KS34465A or Keithley DMM6500 to monitor the DC bias across the diode DUT with proper isolation so as not to affect the capacitance measurements.
We've been doing semiconductor chip design and testing for a long long time, from advanced ADCs, to the 1st MW Silicon Single Chip receiver, 1st RF SoC, 1st Ad-Hoc RF Networking Transceiver (MESH), to 2nd most complex chip DARPA had done (CLASS), and quite a few others I can't mention. Used various leading CMOS fabs, IBM SiGe BiCMOS (7,8,9HP), Bell Labs CBICV2, even InP, so we know what we are doing, even in retirement
Best,
What letter suffixes does JEDEC define?
Usually just -A, -B, etc. for I assume incremental or process improvements, possibly die shrink sort of stuff.
1N4148W is an SMT, not at all possibly compatible with a 1N4148 -- I would comfortably assume the -W is a wholly separate part created by manufacturers, in a nod to the original, but in no way dependent upon its spec.
For sure, I mean, there's 2N7000, but not 2N7000W (or whatever suffix one might use for SOT-23), nor MMBT7000; but 2N7002, an entirely different part number, is in the JEDEC system, for an identical(?) electrical spec with different package.
Interestingly, there's a MMBT7002 from a handful of small manufacturers, so it seems.
MMBT I don't know the history of, but for sure it's not JEDEC's normal numbering system.
As for JEDEC electrical parameters -- even when given, they're usually notoriously loose. Consider 2N2222 fT. Only min is given. No constraint is provided, it could be anything. It probably wouldn't be economical to supply RF dice under this number -- but it wouldn't violate the spec, assuming everything else is met. (Which, for this particular example, I suppose some kind of transistor with same doping level and abruptness, thus same voltage limits, but finer interdigitation would be needed to give a concerningly high (600MHz+?) fT? Or, any interdigitation at all, really, given most 2222s just use a blob or star sort of pattern.)
So, if they don't spec on trr or Cjo, yeh, it's technically correct. Shite spec, but technically correct.
You've done quite a lot of semi work, I'm guessing just not with such bog standard parts, or with standards the likes of JEDEC?
That or most of this shit is so old (1960s, over half a century ago!) it was long settled by the time you, even joined the workforce maybe? Hah. (Well maybe not that old comparatively, you're retired now wasn't it? So most of this was probably concurrent eh, nevermind.)
Tim