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Old 3rd May 2010, 04:50 AM   #1
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Default Amp circuit with 2SJ50 & 2SK135

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
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Old 3rd May 2010, 06:29 AM   #2
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i got a few my shelf..... i could actually be interested in the hitachi original application ...can anybody point us the article ???
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Old 3rd May 2010, 07:35 AM   #3
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Default Original paper

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
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Old 3rd May 2010, 07:38 AM   #4
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good !!!! can we have a schematic please ??
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Old 3rd May 2010, 08:21 AM   #5
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Hi everyone,
After a quick google, I've just found these two circuits apparently from Elektor in the 1980's. Click the image to open in full size.
and
Click the image to open in full size.
Just visit this link and scroll down to post #70 for more info.
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Old 3rd May 2010, 10:14 AM   #6
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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
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Old 3rd May 2010, 05:07 PM   #7
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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.
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Old 3rd May 2010, 05:58 PM   #8
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generic Hitachi schematic - look for recent Sugden 25 thread
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Old 3rd May 2010, 06:01 PM   #9
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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
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Last edited by event horizon; 3rd May 2010 at 06:03 PM. Reason: typo
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Old 3rd May 2010, 06:13 PM   #10
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Attached Images
File Type: jpg Hitachi-amp1.jpg (57.4 KB, 1429 views)
File Type: jpg Hitachi-amp2.jpg (71.9 KB, 1350 views)
File Type: jpg Hitachi-amp3.jpg (68.4 KB, 1329 views)
File Type: jpg Hitachi-amp4.jpg (62.5 KB, 411 views)
File Type: jpg Hitachi-amp5.jpg (54.9 KB, 813 views)
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