Borbeley 60W Mosfet Amp and Hitachi Mosfets
kw...@freenet.edmonton.ab.ca
I have used the Hitachi J50 and K135 in one of my designs. They did work
fine. However I always think that the construction of these mosfets are
rather strange, because their source terminals are connected to case
while all other power devices, either bjt or mosfet, have their collector
or drain connected to case. These mosfets also do not have the high
frequency response as modern vertical power mosfet, though it is probably
hardly noticeable in audio band. I now use IR's irf240 and irf9240. But
they have much higher threshold than the Hitachi's.
--
KWOK MAK email: kw...@freenet.edmonton.ab.ca
EDMONTON, AB
Mithat Konar
> I have used the Hitachi J50 and K135 in one of my designs. They did work
> fine. However I always think that the construction of these mosfets are
> rather strange, because their source terminals are connected to case
> while all other power devices, either bjt or mosfet, have their collector
> or drain connected to case. These mosfets also do not have the high
> frequency response as modern vertical power mosfet, though it is probably
> hardly noticeable in audio band. I now use IR's irf240 and irf9240. But
> they have much higher threshold than the Hitachi's.
Nor do they have the advantageous thermal characteristics of the Hitachi
Devices. The popular Hitachi devices need no thermal compensation to
prevent thermal runaway.
FWIW, about a year ago I spoke to a Hitachi applications engineer about
their family of power MOSFETs and was told that they were no longer
"actively marketed in the US." Just a few months ago I received word from
International Rectifier that IR doesn't support their power MOSFETs for
linear (i.e. non-switching) applications. Neither of these bits of news
make me very happy as I really like MOSFET output stages.
___________________________________________________________________
Mithat Konar director of engineering
biro technology p.o. box 582 / circle pines, mn 55014 / usa
e-mail bi...@ANTISPAMwinternet.com
www www.winternet.com/~biro/
voice/fax 612.786.6643
___________________________________________________________________
Daniel J. Marshall
Hi,
Well, this info came just in time for me. My Soundcraftsman PCR800 amp
bit the dust recently and I just started checking it out and found that
both 2SK135s were bad in one channel. Yesterday, I found equivalent
devices locally, or so I thought, IRF230s. Not having the data sheet
for the 2SK135s or the amp schematic, I had not noticed that the source
was connected to the case. The IRF230s, of which I just purchased four
units have the drain connected to the case. Well, this pretty well
shoots that idea out of the water. It is a nice amp and I would rather
not butcher it by making circuit board mods. It has the output device
cases all connected directly to the heat sink with the leads extending
through and soldered into a printed circuit board.
So, it seems that the best solution would be to locate a pair of the
SK135s (hopefully a matched pair) instead of attempting to find an
equivalent replacement part. Would you (or perhaps others) have a pair
you would be willing to part with?
Dan Marshall
kw...@freenet.edmonton.ab.ca wrote:
>
> I have used the Hitachi J50 and K135 in one of my designs. They did work
> fine. However I always think that the construction of these mosfets are
> rather strange, because their source terminals are connected to case
> while all other power devices, either bjt or mosfet, have their collector
> or drain connected to case. These mosfets also do not have the high
> frequency response as modern vertical power mosfet, though it is probably
> hardly noticeable in audio band. I now use IR's irf240 and irf9240. But
> they have much higher threshold than the Hitachi's.
>