Amp circuit with 2SJ50 & 2SK135

[Conehead]

Hello all,
I still have a few Hitachi MosFet's lying around. They are 4x n-channel, 4 p-channel. I understand those are rather old and were used in the mid 80'ies. So I'm thinking to put them to work and build an AMP out of them. Does anybody know a good quality circuit with discrete Parts (no IC, chips - op amp) for them?

Thanks

[sakis]

i got a few my shelf..... i could actually be interested in the hitachi original application ...can anybody point us the article ???

[PhaseLockLoopy]

Hi Guys

In my collection, I have the original paper by Tohru Sampei, Shin-ichi Ohashi from Hitachi 1977

The ubiquitous seminal Power MOSFET 100 Watt is in the paper fully explained
If this helps PM me

[sakis]

good !!!! can we have a schematic please ??

[jackand08]

Hi everyone,
After a quick google, I've just found these two circuits apparently from Elektor in the 1980's.
and

Just visit this link and scroll down to post #70 for more info.

[Conehead]

Thanks Jackand08,
Nice Job finding those I remember that a friend rebuilt some design from the Elektor Magazine back in the 80's. I think it was called the "Crecendo". But he had massive trouble with self oscillations maybe due to some inductive parts used or simply because of a weak design. I wonder if the schematics is one of those?!

Reg.
Conehead

[jackand08]

You're welcome.

Yes, you're right, if you follow the link to the forum post, one of them is the crescendo (the bottom picture posted) and the other is the mini-crescendo (the top picture posted) with 140 and 70 watt outputs respectively.

I do remember as I was looking round for the schematics, there was a mention about the amp not being very stable and not even a particularly good amp anyway but that's not to say that you could try building one . The link to the forum post in my previous post has a bit more information and some opinions about the amp.

[Zen Mod]

generic Hitachi schematic - look for recent Sugden 25 thread

[event horizon]

It probably wasn't that stable as there was no dominant pole It relied on the input capacitance of the mosfets to reduce the gain at high frequencies, not a clever idea imo as these vary due to voltage accross the devices.

Increase the open loop gain & give the thing a pair of drivers for the mosfets & a couple of miller capacitors & it should be fine

I always fancied building the crescendo, never got round to it though, then went off in another direction entirely

[Zen Mod]

......