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Old 23rd November 2001, 12:32 AM   #1
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I have built a amplifer using exicon mosfets ECX10P16
and ECX10N16 however i had problems with oscilation. Prob due to pcb layout ect. Can anyone help with a suitable circuit and board layout, just a basic design 100W, as i have bought some more and trying to avoid another disaster
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Old 23rd November 2001, 03:40 AM   #2
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these are lateral mosfets ..... make sure u take this into consideration.

the original hitachi design works very well with these devices and can be scaled quite easily .... just use current sources in it instead of plain bais resistors.
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Old 23rd November 2001, 04:49 AM   #3
walker is offline walker  Australia
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Stuart, I am familiar with the devices but have never used them in an amp. Hope this is of help, keep the leads/tracks to and from the FETs as short as possible, some people fit ferrite beads to the gates to control oscillations.

Regards WALKER
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Old 23rd November 2001, 07:13 AM   #4
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Default quick replies!!

i went to bed late up early didnt expect replies so quick. thanks for the replies, the design and pcb i used was from a Penfold book, it was to use Hitachi T03 mosfets, mounted off the board, the reason i used the plastic exicon ones was the original devices were unavailable and the heatsinks i already have were more suited to the plastic devices. As far as oscilation goes i did find when i placed a 0.1uF cap from the 2 junctions which go to the speaker to ground the oscilation stopped. Not sure how this would affect the output though. However the reason i destroyed the devices was too many crock clip leads scope probes ect and then a short. i have 2 more pairs now. So if there is a design \ layout for these and someone can point me in the right direction i would be pleased. The amplifer is only for disco use, quantity is more important than quality. I have decided to try one of the older ETI designs which i have the board layouts for, mainly for some experience and the output devices are one tenth of the cost. Thankyou Stuart
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Old 23rd November 2001, 12:39 PM   #5
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Stuart,

I gather that you might have mounted the devices on the heatsink and used fly-leads to connect to the PCB. In that case, you would most probably encounter oscillations. If your PCB design allows this, connect the gate resistors directly to the Gate pin rather than through the track on the PCB.

Since you mention quantity rather than quality, whatever design you might finally adopt, you would need atleast two pairs for each channel.

Good options to try are: (1) an old design from Electronics Today Internations by David Tilbrook. Can be considered a benchmark of an amp even by today's standards. (2) OPTIMOS design from Seal Electronics.

Both the above amplifiers will not only deliver the quantity that you are looking for but also very high quality.

By the way, are these devices easily available and for how much? Hearing so much about them of late, that I woud like to try out the Exicons myself.
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Old 23rd November 2001, 12:53 PM   #6
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between about 6 and 9 each (ie. per device) which equates to between US$8 and US$13 ........ looked at the Exicons but quickly realised that i can get the HEXFET's for less than 1/2 the price..... lateral mosfets are good dont get me wrong ...... but i dont know that they are 2-3 times better

[Edited by AudioFreak on 11-23-2001 at 08:07 AM]
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Old 23rd November 2001, 01:26 PM   #7
Geoff is offline Geoff  United Kingdom
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Stuart

An Exicon Application Note containing a couple of schematics for 100 to 500W into 4ohm amplifiers can be found on this site:

http://www.profusionplc.com/static/index.htm

Sam

The current prices of the Exicon devices is at the same site.

Geoff
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Old 23rd November 2001, 09:27 PM   #8
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Default exicon

thanks for the replies, best forum i have used. the information is correct re the mosfets, i did get them from profusion. well i do have two pairs already, (not to blow i hope this time). I can etch my own boards, have had a etching tank for a long time, use photo sensitve board, i use tracing paper for the art work works very well. i have profusions catalogue here too, and they sell a evaluation board, and i have the circuits too. i was hoping for some ready done artwork, but perhaps i will have to do my own.

i dont have the two (i think ETI articles, cant see the replies at the moment), perhpas i could find them on the net.

i have enough bits now for some of the older ETI designs now, using transistors i will make some this weekend, like a say they are cheaper to blow, 30P-50P a time.

thannks for all your help, if anyone has some artwork they could scan from old magazines ect it would help. stuart@morgan69.screaming.net
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Old 23rd November 2001, 09:30 PM   #9
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and yes i did use leads to the mosfets, and i mounted the gate resistors direct to the gates, started at 100ohm and up to 1K still oscilated, did have some helpful advice from profusion re gate resistors. the design i used was from a book by Penfold
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