I have some matched p channel mosfets and show a vgs of ~4.6v at 1.3a(until here I have the curves in the graph). I want to run teo of these in parallel with 1.6a on each thus a total of 3.2a. At 3.2a my tokins will have 3v and 3.5v as vgs which should be ok.
Now as a conclusion I think that if you are on the Lower side(-4v) with the vgs of the tokin it could help you if you increase the bias (until you reach the minimum voltage that the optocoupler needs to work properly) because it lowers vgs of tokin and increases vgs of irpf. Please correct me if I misunderstood it somehow. Also implied hardware should support the increased bias and the output devices should remain in the soa.
i picked up a sheet from ebay
Keratherm 50mm x 50mmx 0.5 mm GPU CPU Heatsink Cooling Thermal Conductive Pad | eBay
Keratherm 50mm x 50mmx 0.5 mm GPU CPU Heatsink Cooling Thermal Conductive Pad | eBay
I will be building Zen Mod's SissySit so I do not want to go beyond 2A, and will not be paralleling devices.
Lowering Vgs (less negative) to suit the p channel mosfet will increase Id above 2A and I do not want to do that.
I don't know all the theory so I cannot comment further.
However, I bought four THF-51Ss and three of them meet Zen Mod's requirements so at least I can build one amp.
Lowering Vgs (less negative) to suit the p channel mosfet will increase Id above 2A and I do not want to do that.
I don't know all the theory so I cannot comment further.
However, I bought four THF-51Ss and three of them meet Zen Mod's requirements so at least I can build one amp.
http://www.crydom.com/en/products/catalog/hsp-series-thermal-pads.pdf
Thanks Dennis!
Haha Mouser is twice cheaper if compare with Digi-Key price
Thanks for the feedback on the thermal pad question guys. I was poking around Mouser too.
The Kerafol Keratherm they sell in the DIY store as a benchmark for comparison looks like its .25 thickness with a .09 C/W rating. Haven’t found a source yet that I could buy from in sheet form.
That eBay link for .5mm sheet is an option I suppose, but at $6 each plus shipping there are others.
I’m trying to decide if I should just grab some of those standard Wakefield-Vette pads that are big enough for the THFs. They’d give .1C/W at 100PSI (wonder if its possible/desirable to get that pressure in this application). I suppose if they do the job one can’t complain for the price.
The other option I was looking at was a 9” X 9” sheet of this Laird product that Mouser lists.
https://www.mouser.com/ProductDetail/Laird/A15727-00?qs=sGAEpiMZZMsiS1%252bJOF5PnwK1iNA68d4INe2jHMyAJwk%3d
It looks to be comparable to the Keratherm C/W. At $30 It isn’t the cheapest option, but I would have enough for more projects. Anybody ever try it?
The Kerafol Keratherm they sell in the DIY store as a benchmark for comparison looks like its .25 thickness with a .09 C/W rating. Haven’t found a source yet that I could buy from in sheet form.
That eBay link for .5mm sheet is an option I suppose, but at $6 each plus shipping there are others.
I’m trying to decide if I should just grab some of those standard Wakefield-Vette pads that are big enough for the THFs. They’d give .1C/W at 100PSI (wonder if its possible/desirable to get that pressure in this application). I suppose if they do the job one can’t complain for the price.
The other option I was looking at was a 9” X 9” sheet of this Laird product that Mouser lists.
https://www.mouser.com/ProductDetail/Laird/A15727-00?qs=sGAEpiMZZMsiS1%252bJOF5PnwK1iNA68d4INe2jHMyAJwk%3d
It looks to be comparable to the Keratherm C/W. At $30 It isn’t the cheapest option, but I would have enough for more projects. Anybody ever try it?
@ Chromenuts
Check if is not too small
@
and Diyers
One question :
What performance choice between 3 options :
1|
top notch quality arctic silver goop and large keratherm sheet = $$
with moderate size heat sink ?
2|
goop paste and mica or rubber pads , relay etc = moderate price
with big size $uperb quality heat $ink ?
3| $$$$$ilionaire ?
Check if is not too small
@
and DiyersOne question :
What performance choice between 3 options :
1|
top notch quality arctic silver goop and large keratherm sheet = $$
with moderate size heat sink ?
2|
goop paste and mica or rubber pads , relay etc = moderate price
with big size $uperb quality heat $ink ?
3| $$$$$ilionaire ?
it doesnt't matter what type of thermal interface you have - you need to get rid of , say , 100W of heat ...... do not forget poor small mosfet ....... keratherm T0247 pad is sorta necessary to keep it well and alive
so , heatsink need to be of proper and healthy performance
SIT is so damn big , so even cheap and crude thermal interface will do the job , contrary to mosfet side
so , heatsink need to be of proper and healthy performance
SIT is so damn big , so even cheap and crude thermal interface will do the job , contrary to mosfet side
I believe that Arctic Silver is electrically conductive. I had to replace it with Arctic Alumina...
Interesting findings when I measured my THF51-S tonight
The 2 I bought from Pras measure VGS = -3.4 and -3.5 respectively for Iq of 1A8 at 19V while the 2 I got from Tomo measure -1.8 and -1.6 at the same current and drain voltage.
Happy Days are coming ..dB
100W of heat per channel , nominally
say that you have 22V5dc rails , and 2A Iq , that's 45V x 2A = 90W of heat
Modushop's Pesante Dissipante 4U/400 is swiss knife solution for FW amps format
enough meat to cool it off , enough space for dual mono , if you choose it
4U/300 is ...... sorta FW amp in iPod case
For TO-247 mosfet clamp can do case thermal extension or better solution not clamp but small heat sink on external side. This one on the right photo is TO-220 format show only for example
Attachments
I have been in discussions with watanabetomoaki of ebay regarding the Vgs measurements of the THF-51S that I had purchased from him. His test method was different from the one shown by Zen Mod. He has asked me to pass on the following message:
"I have been requested only by SIT of the same characteristics from many members of this forum. Thank you.
I did not include such strict matching fee for my listing, but at first I was receiving favorably.
However, too many people made the same request, and even complaints about the accuracy of screening came.
In this state, in the near future I will not be able to continue similar services.
Anyway, no so much stock anymore ...
However, I also made a mistake. That is, there are several sorted by connecting drain and source in reverse.
That was happend when the buyer directly requested the determined Id value.
In principle, the FET has no polarity at drain and source. Of course, this FET does not have built-in protection diodes like MOS type ones.
So, drain and source may be either. So, why do you specify it? That is because, of course, the value of Id is not symmetrical at all.
Naturally, as a manufacturing company, because typical characteristics are shown, general polarity designation is necessary.
However, there is no necessity for measuring the characteristics data sheet with DIY and using it.
So, in order to get closer to the Id value that the purchaser wished, the person who specified the Id value,I have measured the metal case as GND.
I think that it is my only mistake to have a case where I forget to tell him that.
So, if you received the SITs those characteristics are very different, measure the drain and source by exchanging it and use it."
"I have been requested only by SIT of the same characteristics from many members of this forum. Thank you.
I did not include such strict matching fee for my listing, but at first I was receiving favorably.
However, too many people made the same request, and even complaints about the accuracy of screening came.
In this state, in the near future I will not be able to continue similar services.
Anyway, no so much stock anymore ...
However, I also made a mistake. That is, there are several sorted by connecting drain and source in reverse.
That was happend when the buyer directly requested the determined Id value.
In principle, the FET has no polarity at drain and source. Of course, this FET does not have built-in protection diodes like MOS type ones.
So, drain and source may be either. So, why do you specify it? That is because, of course, the value of Id is not symmetrical at all.
Naturally, as a manufacturing company, because typical characteristics are shown, general polarity designation is necessary.
However, there is no necessity for measuring the characteristics data sheet with DIY and using it.
So, in order to get closer to the Id value that the purchaser wished, the person who specified the Id value,I have measured the metal case as GND.
I think that it is my only mistake to have a case where I forget to tell him that.
So, if you received the SITs those characteristics are very different, measure the drain and source by exchanging it and use it."