Here is a new thread, because I haven't seen one quite like this before.
I am proposing a project to design a BJT transistor tester that can do reliable matching and that can handle small signal all the way to power transistors. Also it should be able to do a non-destructive test for secondary breakdown on power transistors.
What I have in mind should not cost too much, be linked up to a computer, via USB preferably, and all the processing would be software based. It should allow to save all the test result data, do comparisons of multiple parts, such as combining curves into a single plot, and each part having its test data saved, could be recalled individually to be compared with others at any time.
I envision a tester with a sizable heatsink, on which both NPN and PNP could be tested at the same time, and in pairs (of each). For example a pair of NPNs could be tested to match them, or a pair of PNPs, or 2 pairs of each at the same time, so not only 2 NPNs and 2 PNPs could be tested for matching together, but also at the same time the pair of each sex could be tested for matching as a whole set of 4 parts.
I would put a good temperature sensor on the heatsink at each transistor location, so the test temperature could also be known, recorded along with it, and also the temperature of all present parts could be watched for equalization. Since all the parts would be on the same heatsink, they should eventually come to close to a temperature equilibrium so all parts would then be tested together at the same time at a similar enough temperature.
A "pre-test" delay could be afforded and monitored by software, giving the parts a certain somewhat minimal power to dissipate for a while, to bring them to a certain level, so they could be tested at a determined temperature.
I believe this should not be too difficult to achieve with a simple enough circuitry and all handled by software.
Both the secondary breakdown and matching could be done at a determined temperature.
I would not want a design that uses exotic parts or overly difficult or expensive parts. It must be easily buildable by any diyer, anywhere on the planet.
Being able to test power transistors with a different package, by sets of up to 4, and on the same heatsink, will require a little thinking, but I'm sure we can come up with something clever.
To keep it cheap and simple on the electronic side, I think making use of an arduino board might be a good idea, but there may be other choices usable. The arduino would allow easy USB without having to design all that interface circuitry, and it should have enough I/O ports to handle all of the tester's function. If an arduino nano isn't enough for example, there are larger models with more ports.
For the small signal parts, there could be various sockets to accommodate the various packages, and at least they should also be tested in pairs at a minimum, but more could be tested for matching at the same time.
Anything with a package mountable on a heatsink should be. Including the TO-126, TO-220, etc... Which might make for a trick heatsink design, but worth the effort.
I have come across a very interesting design, I think by a chinese guy, that does a good part of what I'm looking at doing. His is linked to a computer, windows only, and does plot curves, for matching, and saves the data, but only one part at a time, doesn't do any non-destructive second breakdown test, doesn't use a heatsink, and so it doesn't allow tests at pre-determined temperatures.
There is also that excellent (a bit older now) application note AN930 from motorola, that is only for a second breakdown tester, non-destructive, but that is only aimed at being used with an oscilloscope, so it doesn't allow recording of any data, doesn't allow for matching and doesn't work with a computer.
I believe this kind of tester would allow easy and reliable testing/matching, hopefully not cost too much, offer more features than available out there, and would be likely to suscitate quite some interest from many diyers (like me first).
I wouldn't be able to handle all the design by myself, so I'm hoping for a collaborative work.
And perhaps, a well designed device with all the trimmings could also become something that could be sold on the diyaudio store...
I am proposing a project to design a BJT transistor tester that can do reliable matching and that can handle small signal all the way to power transistors. Also it should be able to do a non-destructive test for secondary breakdown on power transistors.
What I have in mind should not cost too much, be linked up to a computer, via USB preferably, and all the processing would be software based. It should allow to save all the test result data, do comparisons of multiple parts, such as combining curves into a single plot, and each part having its test data saved, could be recalled individually to be compared with others at any time.
I envision a tester with a sizable heatsink, on which both NPN and PNP could be tested at the same time, and in pairs (of each). For example a pair of NPNs could be tested to match them, or a pair of PNPs, or 2 pairs of each at the same time, so not only 2 NPNs and 2 PNPs could be tested for matching together, but also at the same time the pair of each sex could be tested for matching as a whole set of 4 parts.
I would put a good temperature sensor on the heatsink at each transistor location, so the test temperature could also be known, recorded along with it, and also the temperature of all present parts could be watched for equalization. Since all the parts would be on the same heatsink, they should eventually come to close to a temperature equilibrium so all parts would then be tested together at the same time at a similar enough temperature.
A "pre-test" delay could be afforded and monitored by software, giving the parts a certain somewhat minimal power to dissipate for a while, to bring them to a certain level, so they could be tested at a determined temperature.
I believe this should not be too difficult to achieve with a simple enough circuitry and all handled by software.
Both the secondary breakdown and matching could be done at a determined temperature.
I would not want a design that uses exotic parts or overly difficult or expensive parts. It must be easily buildable by any diyer, anywhere on the planet.
Being able to test power transistors with a different package, by sets of up to 4, and on the same heatsink, will require a little thinking, but I'm sure we can come up with something clever.
To keep it cheap and simple on the electronic side, I think making use of an arduino board might be a good idea, but there may be other choices usable. The arduino would allow easy USB without having to design all that interface circuitry, and it should have enough I/O ports to handle all of the tester's function. If an arduino nano isn't enough for example, there are larger models with more ports.
For the small signal parts, there could be various sockets to accommodate the various packages, and at least they should also be tested in pairs at a minimum, but more could be tested for matching at the same time.
Anything with a package mountable on a heatsink should be. Including the TO-126, TO-220, etc... Which might make for a trick heatsink design, but worth the effort.
I have come across a very interesting design, I think by a chinese guy, that does a good part of what I'm looking at doing. His is linked to a computer, windows only, and does plot curves, for matching, and saves the data, but only one part at a time, doesn't do any non-destructive second breakdown test, doesn't use a heatsink, and so it doesn't allow tests at pre-determined temperatures.
There is also that excellent (a bit older now) application note AN930 from motorola, that is only for a second breakdown tester, non-destructive, but that is only aimed at being used with an oscilloscope, so it doesn't allow recording of any data, doesn't allow for matching and doesn't work with a computer.
I believe this kind of tester would allow easy and reliable testing/matching, hopefully not cost too much, offer more features than available out there, and would be likely to suscitate quite some interest from many diyers (like me first).
I wouldn't be able to handle all the design by myself, so I'm hoping for a collaborative work.
And perhaps, a well designed device with all the trimmings could also become something that could be sold on the diyaudio store...
This guy (locky_z) here, did a nice job with his curve tracer:
http://www.diyaudio.com/forums/solid-state/151253-diy-curve-tracer-pc.html
It's in the spirit of what I have in mind more or less.
He's using a pc lpt port and it's windows only. Plus it's just a curve tracer, although it should be good enough for matching. It doesn't do power transistors in the way I describe and only does one part at a time. But this can also be an inspiration.
I would make something more universal, in regards to the computer being used, so it could work on linux/unix/mac as well and use a more universal connection: USB
I wouldn't bother with mosfets, jfets or whatever types of fets. Those should test quite well on his current design, although it doesn't work on anything else besides windows. This can keep the design simpler by restricting to bjts only.
http://www.diyaudio.com/forums/solid-state/151253-diy-curve-tracer-pc.html
It's in the spirit of what I have in mind more or less.
He's using a pc lpt port and it's windows only. Plus it's just a curve tracer, although it should be good enough for matching. It doesn't do power transistors in the way I describe and only does one part at a time. But this can also be an inspiration.
I would make something more universal, in regards to the computer being used, so it could work on linux/unix/mac as well and use a more universal connection: USB
I wouldn't bother with mosfets, jfets or whatever types of fets. Those should test quite well on his current design, although it doesn't work on anything else besides windows. This can keep the design simpler by restricting to bjts only.
Good to hear you want to start something like that, you can count on me for crowd funding 
. I have Locky's curve tracer, and couldn't live without anymore. It is USB by the way.
Not including FETS would be a BIG miss. Matching is a key use/objective of such devices for us audio folks, and FETs are as much used and matched as BJTs, think of differential input stages for example. So please don't discard that.
What I would be looking for in any case is a real high voltage / high current tester to really test power output devices, say up to 100 volts and 10 amps. Yep, that will be a very hefty transformer.
Mounting and measuring multiple DUTS at the same time needs some thinking about the casing touching the heatsinks (TO-3); and I agree with you that comparison (matching) should be done under strictly same body temperature, hence solid heat sinking and fixation. Lucky's curve tracer is missing this and I have considered several times to install sort of quick-clamp heatsink, as the DUTs heat up during test. Though, why measure the temperature if all devices are then measured on the same heat sink (same temperature), if you cannot change the heatsink temperature anyway?
. I have Locky's curve tracer, and couldn't live without anymore. It is USB by the way. Not including FETS would be a BIG miss. Matching is a key use/objective of such devices for us audio folks, and FETs are as much used and matched as BJTs, think of differential input stages for example. So please don't discard that.
What I would be looking for in any case is a real high voltage / high current tester to really test power output devices, say up to 100 volts and 10 amps. Yep, that will be a very hefty transformer.
Mounting and measuring multiple DUTS at the same time needs some thinking about the casing touching the heatsinks (TO-3); and I agree with you that comparison (matching) should be done under strictly same body temperature, hence solid heat sinking and fixation. Lucky's curve tracer is missing this and I have considered several times to install sort of quick-clamp heatsink, as the DUTs heat up during test. Though, why measure the temperature if all devices are then measured on the same heat sink (same temperature), if you cannot change the heatsink temperature anyway?
Good to hear you want to start something like that, you can count on me for crowd funding
Glad to "hear" that!
What he's done is very nice and helpful, but I need more and I want it more universal as far as platform. I do not use windows.
I forgot about that, I was thinking about his first incarnation.
Well, I think this can be done if we make it "modular", so those who don't need to work with fets don't need to build that part of it. I'm quite sure we can come up with some clever way of doing this.
Absolutely!! My thoughts exactly. We should be able to test those modern types with voltages over 350V.
Maybe not! I would go for switching psu for that. Much smaller and likely cheaper if we can find a way to use commercially available units, if feasible.
But then again, there are ways to make good switching psus without spending too much. I used ICs before that are specialized for this, the SG3524, which make it possible to make them with a fairly low part count. The one thing I don't like about switching psus are those "wierd" transformers. They are small and light, but I'm not sure they can be found easily...
Yes, the issue doesn't come up when we're only working with same sex types, but we must isolate when mixing sexes unfortunately.
BUT!!! I may be wrong, but there may still be a way, if someone can confirm this: I think we might be able to put all the collectors' potential together, so we could forget about the isolation. This isn't possible in an amp, although some amps are designed with all collectors together, even in a complementary topo, but those are either at ground or the amp's output...
It would really be a plus if we avoid insulation, not only it would reduce the thermal resistance, it would also make it much easier and more convenient to mount and unmount parts without insulators or worse, grease!
The one big thing that would remain to be careful about if no insulation is needed, is the potentially very high voltage present during testing on the heatsink. So either: do not touch during testing! or put some type of mechanical shield on that sink in case someone still touches it during testing.
It's a must! Those tests are temperature dependent and to avoid doing a half way job, the temperature must be taken into account.
My reasons for temperature sensors on each part are:
1) tests can be done at various pre-determined temperatures
2) the tests results can be recorded for each temperature
It is quite possible to obtain those pre-determined various test temperatures, as I listed in my first post in the wanted features, as we can have the devices dissipate some power before testing, up to the pre-determined wanted temperature, wait for it to stabilize and then quickly do the tests while all the parts at at that wanted temperature and before it changes.
I know all this seems a little bit of a tall order, but nothing that can't be done and it doesn't require very advanced engineering to achieve it, and it's a really useful feature that I really want in the tester. Plus since we make a software operated tester, we only need the basic electronics and do most of it with software.
This is going to be a very cool project I think. And I will be very happy with such a device when we make it work.
The features wanted are coming together.
We can make it modular so the testing of parts other than bjts can be done on a separate optional module attached to a main module, so those like me who do not use any kind of fets can opt not to build the option.
Perhaps the bjt testing can itself be a an optional module like the fet testing one, and the requirement would be that at least one module be attached to the main one to function properly.
If done right, other modules could be designed and extend the features to test other types of parts, and perhaps more kinds of tests could be performed later if a updated existing module was designed to add more functions.
One thing to look at, is how to test the power transistors in a way that has all their collectors together, so no insulation would be needed on the heatsink(s).
It should remain as convenient as possible, so the power transistors should be easily mounted, only plugging into a socket and with screws to keep them tightly in place.
It's easy to have safeties built-in regarding overheating, since all parts locations on the heatsink would have a sensor.
Being able to test even the highest voltage parts would be great, like those with Vce of 350 or 400V. Obviously this will require a hefty psu for testing at high currents and being able to reach the high secondary breakdown voltages on such parts. To avoid a huge transformer, a switching power supply seems in order.
The parts' saved test data could be used at a later time for comparisons, so parts matching doesn't have to be done right then and there on the spot with the parts at hand, and this means parts could possibly be matched from remote, for example someone with this tester could test some parts on hand, and share this with someone else, also with the tester, who could be far away, and other parts could be tested and matched...
There is nothing like this on the market that I know of, and I think we can easily get addicted to such a thing.
We can make it modular so the testing of parts other than bjts can be done on a separate optional module attached to a main module, so those like me who do not use any kind of fets can opt not to build the option.
Perhaps the bjt testing can itself be a an optional module like the fet testing one, and the requirement would be that at least one module be attached to the main one to function properly.
If done right, other modules could be designed and extend the features to test other types of parts, and perhaps more kinds of tests could be performed later if a updated existing module was designed to add more functions.
One thing to look at, is how to test the power transistors in a way that has all their collectors together, so no insulation would be needed on the heatsink(s).
It should remain as convenient as possible, so the power transistors should be easily mounted, only plugging into a socket and with screws to keep them tightly in place.
It's easy to have safeties built-in regarding overheating, since all parts locations on the heatsink would have a sensor.
Being able to test even the highest voltage parts would be great, like those with Vce of 350 or 400V. Obviously this will require a hefty psu for testing at high currents and being able to reach the high secondary breakdown voltages on such parts. To avoid a huge transformer, a switching power supply seems in order.
The parts' saved test data could be used at a later time for comparisons, so parts matching doesn't have to be done right then and there on the spot with the parts at hand, and this means parts could possibly be matched from remote, for example someone with this tester could test some parts on hand, and share this with someone else, also with the tester, who could be far away, and other parts could be tested and matched...
There is nothing like this on the market that I know of, and I think we can easily get addicted to such a thing.
And just think, I bought one of these for 24 dollars...
http://www.ebay.com/itm/New-Transistor-Tester-Capacitor-ESR-Inductance-Resistor-LCR-Meter-NPN-PNP-MOSFET-/251334183807?pt=LH_DefaultDomain_0&hash=item3a84af4b7f
And it runs on a 9 volt battery...
That schematic looks like a great place to start, I will help in any way I can...
http://www.ebay.com/itm/New-Transistor-Tester-Capacitor-ESR-Inductance-Resistor-LCR-Meter-NPN-PNP-MOSFET-/251334183807?pt=LH_DefaultDomain_0&hash=item3a84af4b7f
And it runs on a 9 volt battery...
That schematic looks like a great place to start, I will help in any way I can...
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And just think, I bought one of these for 24 dollars...
http://www.ebay.com/itm/New-Transistor-Tester-Capacitor-ESR-Inductance-Resistor-LCR-Meter-NPN-PNP-MOSFET-/251334183807?pt=LH_DefaultDomain_0&hash=item3a84af4b7f
And it runs on a 9 volt battery...
That schematic looks like a great place to start, I will help in any way I can...
Great!
I have something similar to this also, it was less than $20 when I got it on ebay.
It's very convenient and it does a lot of things, but it won't do all those things I'm looking for, so that's why I'm digging into this.
I want it linked to a computer, and besides locky_z's excellent tester, I haven't seen anything out there that does what I'm looking for.
I'm sure a good collaborative work can work well and we can achieve this.
I'm afraid some commercial entity will later grab on to this idea and put something out on the market, but that may take a while.
Here is what I'm thinking we could do:
- A main root module that can receive one or more optional module attachment
this main module could very well be for example an arduino, since it already has the usb port built-in, is very cheap and has communication protocol already built-in as well. I'm not yet familiar with arduino, so I'm not sure how a separate software could use the arduino built-in communication protocol for its own purpose and properly interface with the arduino software loaded into it.
- a switching psu with enough umph to provide all the various needed voltages for the modules and the test voltages and currents.
- a module for bjt testing, with heatsinks and all that.
- a module for fet testing. the mosfets would also need a heatsink if they are to be tested at high power levels.
A good method for attaching modules to each other has to be devised so more than one optional module can be attached to the same root module. Avoiding bad contacts is not an option!
I have a couple of arduino nano boards and also an uno, but I haven't yet done much besides basic stuff on them, mostly tutorials to learn the abcs of it, but nothing yet to know enough to make full use of it.
If someone has a better idea than using arduino as a base, please share your thoughts.
- A main root module that can receive one or more optional module attachment
this main module could very well be for example an arduino, since it already has the usb port built-in, is very cheap and has communication protocol already built-in as well. I'm not yet familiar with arduino, so I'm not sure how a separate software could use the arduino built-in communication protocol for its own purpose and properly interface with the arduino software loaded into it.
- a switching psu with enough umph to provide all the various needed voltages for the modules and the test voltages and currents.
- a module for bjt testing, with heatsinks and all that.
- a module for fet testing. the mosfets would also need a heatsink if they are to be tested at high power levels.
A good method for attaching modules to each other has to be devised so more than one optional module can be attached to the same root module. Avoiding bad contacts is not an option!
I have a couple of arduino nano boards and also an uno, but I haven't yet done much besides basic stuff on them, mostly tutorials to learn the abcs of it, but nothing yet to know enough to make full use of it.
If someone has a better idea than using arduino as a base, please share your thoughts.
As much as possible software based was the main goal from the start. This makes for simpler hardware and a much more flexible and easily update-able device. More features may even be added later with software.
And making it modular also allows adding even more features without changing everything.
There should be no need for extensive firmware, as most of the software can run on the computer, but I think there might be a need to have some mechanism to have the main software send some type of "macros' to the device, that would be run locally and send resulting data back. It seems there may be some usb delays in communication that could prevent the main software on the computer to manipulate in real time all the features on the device. I'm not certain about this, but I think our friend locky_z ran into such limitations.
This is a rather extensive project, and I think the more collaborators work on it, the better. The tester designed by locky_z has found a serious audience and this project goes beyond the features his tester has. I am really looking forward to getting this put together. I need this for my amp projects.
Working on several projects, plus my regular work, doesn't leave much time to make fast progress on all projects.
I will want to use something like this described here for my amps projects, so I wish this could move forward at the same time.
I was thinking about this: Why not make it an open source project, just like many others, mostly software, but there are also hardware open source projects out there.
I have no experience in open source and coordinating such things. But I will do whatever I can.
Has anyone any interest in this project? With any experience managing/coordinating? And/or contributions to make?
This could end up as something to put on the diyaudio store, so it should be universal, well made and for anyone to use.
I will want to use something like this described here for my amps projects, so I wish this could move forward at the same time.
I was thinking about this: Why not make it an open source project, just like many others, mostly software, but there are also hardware open source projects out there.
I have no experience in open source and coordinating such things. But I will do whatever I can.
Has anyone any interest in this project? With any experience managing/coordinating? And/or contributions to make?
This could end up as something to put on the diyaudio store, so it should be universal, well made and for anyone to use.
And it runs on a 9 volt battery...
That schematic looks like a great place to start, I will help in any way I can...
Hi, it's been a while, and I've been kept away from the hobby for too long. I'm thinking again about this thing.
I was wondering if you had that schematic, since you mentioned it. I'd be curious to see it, and perhaps get some inspiration from it.
Maybe this could be used as a base and other features could be added, if feasible. Otherwise it can still be an inspiration to get one started with something else.
One thing that I really want to get is a second breakdown tester, as much as one to match up parts. Grabbing data from measurements, send it all to a computer for analysis, trace some curves, run comparisons by software, superimpose curves from multiple parts to see visually how they match...
Loads of software to write I'm sure. But first, if we could get the hardware put together, that'd be great.
Good to hear you want to start something like that, you can count on me for crowd funding
Not including FETS would be a BIG miss. Matching is a key use/objective of such devices for us audio folks, and FETs are as much used and matched as BJTs, think of differential input stages for example. So please don't discard that.
What I would be looking for in any case is a real high voltage / high current tester to really test power output devices, say up to 100 volts and 10 amps. Yep, that will be a very hefty transformer.
Mounting and measuring multiple DUTS at the same time needs some thinking about the casing touching the heatsinks (TO-3); and I agree with you that comparison (matching) should be done under strictly same body temperature, hence solid heat sinking and fixation. Lucky's curve tracer is missing this and I have considered several times to install sort of quick-clamp heatsink, as the DUTs heat up during test. Though, why measure the temperature if all devices are then measured on the same heat sink (same temperature), if you cannot change the heatsink temperature anyway?
Are you still giving any thoughts to this idea?
I was thinking about the power DUTs, which could be put in pairs on the same heatsink, with some kind of socket installed on the heatsink so those big TO3s could just plug in and get tested. Of course they should really be bolted as well, or the heatsink contact wouldn't be that good, and to avoid putting messy grease under the cases to make sure they exchange their heat, although it would still insert some resistance, there are those flexible TO3 insulator shims that could work well.
Maybe there is a way to design the pair testing so they have their collectors in common (we'd have to see about that), so as to not worry about their cases being in contact through the heatsink. Although making the use of those flexible shim insulators would probably permit to avoid that, as long as the screws wouldn't be the ones making the contact.
You could pull this together with several source-measure units from Keithley Keithley Source Measure Units | Tektronix or a Tek 370. Those are seriously expensive solutions. Essentially you need programmable power supplies and meters. The high voltage/high current stuff will be challenging as will testing high power. Are you going to mount the parts to heat sinks? I remember using a gadget that would heat a transistor to a target temperature while on a curve tracer to see/plot the temperature characteristic.
FET's and bipolars just need different polarity on the control element. It should require very little overhead to support.
Matching in a population is easier if you can store the key properties and use the computer to find the best matches.
It would be useful and not difficult to add noise testing while your at it.
FET's and bipolars just need different polarity on the control element. It should require very little overhead to support.
Matching in a population is easier if you can store the key properties and use the computer to find the best matches.
It would be useful and not difficult to add noise testing while your at it.
Not in the cards for most diyers, especially not for me, and not a real "integrated" solutions, simple enough in a single tool, with the software that handles it all in one without having to do loads of manipulations and calculations or processing.
That's most of the needed stuff, but not all.
For the power transistors testing option, that's a must. Although the use of pulses can help minimize the needed heatsinking, and with a temperature sensor on the sink, the software can keep an eye on that and use a duty cycle that prevents overheating. Plus the sensor also provides a means to test all devices within the same range, which can make for much better matching.
Doing the test by software allows choosing a settled temperature on the sink, so all parts are tested the same. Early measured data can just be discarded, although perhaps temporarily displayed on the screen, until the right temperature is reached and settles, then those data points can be recorded.
Yes, and that's why I've been thinking about the "module" feature, for testing the different types of parts, as they can't all be tested using the same jig, especially with the very large disparities in device cases and their size difference, not to mention the ranges of voltages and currents...
My point exactly!
What I'm seeking is a comprehensive one tool system that is specifically made for that purpose and automating as much as possible, and also being able to save the data.
Some manipulations would be needed to keep the tested parts identified once they are tested, perhaps a numbering system managed by the software, that would have to be replicated manually on the parts, so each tested part can readily be identified.
Using software to go through all of the tested parts data is a must, to make the best matching, keep the data and work on a large enough crowd of parts to find the best match combinations.
And when doing small signal transistors for example for dual diff amps, which require 4 matched parts for best results, this can be much easier, especially for the matching of npn to pnp, which can be a very difficult task with those large disparities.
Fortunately, with the small signal parts, they are so much cheaper than power transistors, that it is much more feasible to obtain a much larger samples.
I've been getting such parts in batches of 100 minimum, even if only 4 are needed, so I can increase the chances to land good matches.
Yes, that's a great idea! Probably not too much more hardware to add, and the software can handle the rest.
And just think, I bought one of these for 24 dollars...
http://www.ebay.com/itm/New-Transistor-Tester-Capacitor-ESR-Inductance-Resistor-LCR-Meter-NPN-PNP-MOSFET-/251334183807?pt=LH_DefaultDomain_0&hash=item3a84af4b7f
And it runs on a 9 volt battery...
That schematic looks like a great place to start, I will help in any way I can...
I think a look at that thing's schematic would be likely to give some ideas.
One thing is for sure, something like this running off a 9V battery won't be able to handle any power transistors.
If we want to test SOA on power transistors, a sufficiently high voltage AND current are needed. This would make for a very beefy power source, and that is where some limits have to be placed, otherwise that thing can get expensive and big real quick.
Perhaps there is no real need to be testing beyond some 10A on power transistors, and if we want to be able to test the second breakdown on parts with max vce at some 140V or more, that is definitely a difficult power supply to make.
However, when testing for SOA, when the current is high, voltage is low, and vice versa, so in reality the power may not be always that huge, but still significant if we want to be able to test several points on the SOA limits.
For second breakdown testing, only a very tiny current needs to be supplied, and for a very short time, so that's not too big of a deal, and perhaps that should be its own separate power supply, to keep it safe for those DUT.
Some power transistors have really large SOA nowadays, and I don't think we can make something economical enough that would be able to test the whole range of the SOA. Perhaps there is no real need for full SOA testing anyway, as besides the second breakdown testing, the really needed tests are for part comparisons/matching.
I think in the existing other tools available out there, it's locky_z's curve tracer that is the closest one with the needed features.
It's likely that some of the missing features and options in his tracer probably could be added by just software, without doing anything to his hardware.
But it is missing some features that do require more hardware and perhaps a different approach for some aspects.
And as far as I'm concerned, one huge feature missing, for me personally, is the lack of a mac native version of the software.
It would be nice to be able to compare parts for matching without doing the whole shebang on the curve tracing. Only a few points here and there, properly chosen, would suffice for matching parts, and some way of keeping an eye on temperature would also be a big help.
It's likely that some of the missing features and options in his tracer probably could be added by just software, without doing anything to his hardware.
But it is missing some features that do require more hardware and perhaps a different approach for some aspects.
And as far as I'm concerned, one huge feature missing, for me personally, is the lack of a mac native version of the software.
It would be nice to be able to compare parts for matching without doing the whole shebang on the curve tracing. Only a few points here and there, properly chosen, would suffice for matching parts, and some way of keeping an eye on temperature would also be a big help.
Going in the right direction, but not quite sufficient.
Can't handle the power transistors with their higher currents and voltage is limited to 30V.
Not an easy and fool proof method to match parts, just by plotting curves and visually match, not very accurate.
No way to keep and catalog measurements on parts, to run through comparison software and make the best matches.
Nothing to test second breakdown.
And a bit pricy for the lacking features really needed for the purpose of matching.
Plotting curves looks spiffy, but then when do you do with them if your goal is to match parts the best way?
Some of the features are what's needed, but many are missing.
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