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Old 29th April 2013, 06:04 PM   #1
Boscoe is offline Boscoe  United Kingdom
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Default LME49830 Project/Boards...

So ever since OPC introduced me to the LME amplifier chips I have wanted to make an amp based on them. Unfortunately I was unable to buy the boards he offered and so have designed my own. They work and feature a better heatsink for the LME.

There's an option to run the LME and output stage on separate rails.

Here's some pictures and specs...

Click the image to open in full size.

Click the image to open in full size.

Blue line is 1W,
Green line is 50W

Both were run into 4R, 80KHz bandwidth, 35V rails (LME on the same rail) and at 300mA bias current. This is just with initial component values, I expect to get better performance once I have fiddled and run the LME on higher regulated rails.

Click the image to open in full size.

Click the image to open in full size.

You don't have to use an SMA connector for the input there are just holes there.

If anyone is interested in boards I will get some made. I have had a quick look at prices and for an order of 50 boards I will have to sell them at US$15+postage.

Last time I posted there were a few people interested so to get an idea of a number post your name and the names previous in your post with the number you want.

Thanks
Boscoe
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Old 30th April 2013, 04:01 PM   #2
Boscoe is offline Boscoe  United Kingdom
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Nothing?
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Old 30th April 2013, 04:03 PM   #3
llwhtt is offline llwhtt  United States
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Since it's a chip amp try the chip amp forum.

Craig
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Old 30th April 2013, 04:04 PM   #4
AndrewT is offline AndrewT  Scotland
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A big heatsink. Well done.

What about HF decoupling across the drains of the output devices?
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Old 30th April 2013, 06:17 PM   #5
Boscoe is offline Boscoe  United Kingdom
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A big heatsink. Well done.

What about HF decoupling across the drains of the output devices?
Nothing on the current revision of boards I will add some and see what happens, no ill affects due to the lack of them yet.
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Old 30th April 2013, 07:20 PM   #6
rsavas is online now rsavas  Canada
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I realize that it is a OPC clone, but what if by accident, you get a short on the load side? What protection measures are you incorporating or is this different discussion all together?
Blow a fuse all the way back to the mains fuse?
10uF/50V/1206 COG, bias cap, I bet that ain't cheap. Why 50V? I wonder if you use a X7R, would it make a difference?
I know Bob C. suggested in his book a optional R-C snubber, across the MOSFET Gate Drain?
Gate Zeners? Optional TPC?
Diodes across Drain/Sources?
Just some suggestions.
Rick
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Old 30th April 2013, 07:27 PM   #7
Boscoe is offline Boscoe  United Kingdom
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Quote:
Originally Posted by rsavas View Post
I realize that it is a OPC clone, but what if by accident, you get a short on the load side? What protection measures are you incorporating or is this different discussion all together?
Blow a fuse all the way back to the mains fuse?
10uF/50V/1206 COG, bias cap, I bet that ain't cheap. Why 50V? I wonder if you use a X7R, would it make a difference?
I know Bob C. suggested in his book a optional R-C snubber, across the MOSFET Gate Drain?
Gate Zeners? Optional TPC?
Diodes across Drain/Sources?
Just some suggestions.
Rick
It's not an OPC clone otherwise the board would be a lot like The Wire. The schematic is kept simple which makes it similar to OPC's design.

Use fuses on the outputs of you PSU or output protection off the board.

The bias cap is 100nF 50v NP0/C0G.

I don't think gate zeners are necessary. I haven't really got space for diodes across the outputs!
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Old 30th April 2013, 10:57 PM   #8
rsavas is online now rsavas  Canada
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This is how I have done it, different again. I put two pair of devices in my layout. It i s the bottom layer looking from the top side.
Rick
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Old 16th June 2013, 06:18 PM   #9
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The National Semi prototype boards (for the 2SK1530/2SJ201) are showing up on EBay -- I've found that once an item starts trafficking they come out of the woodwork:

Click the image to open in full size.

Should be easy enough to use with lateral mosfets by rearranging the pinout, or the readily available IRFP or Fairchild devices.
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Old 16th June 2013, 06:31 PM   #10
qusp is offline qusp  Australia
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Quote:
Originally Posted by Boscoe View Post
Nothing?
might have something to do with Owen having updated 4 layer boards for sale again right now
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