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Old 11th November 2011, 03:32 AM   #1
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Default LME49830 like driver chip for Quasi-Complimentary?

Hi,

I want to experiment with silicon carbide static induction transistors (SiliconSouth SJEP120R063A), but they're only available in the N-channel sex. Use of a transformer is out cause I'm targeting 110V rails and want direct coupled.

Could a build-out circuit on the LME49830 be made on the Pout pin for swapping polarity to make it work?
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Old 11th November 2011, 04:26 AM   #2
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Topology-wise it can't this simple as adding Q4, is it? MOSFETs being used in place of a pair of SiTs
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Old 11th November 2011, 05:57 AM   #3
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I do not know anything about electronics, but I think you could make that even simpler...

Click the image to open in full size.

Just an idea... May not work. More intelligent people shall comment.
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Old 11th November 2011, 09:33 AM   #4
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Your answer is in your title.
Read up on quasi complementary. Start with Shaw then work through Baxandall and JLH.
Finally for implementation read Quasi's thread.
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Old 11th November 2011, 09:58 AM   #5
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Quote:
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Read up on quasi complementary.
That's the trouble, I got nothing 'cept for a Dynaco 120A schematic
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Old 11th November 2011, 10:13 AM   #6
AndrewT is offline AndrewT  Scotland
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I just typed "quasi complementary Shaw" into Google and the fist entry is a 1970 paper that shows Shaw and explains.
The second entry is a JLH article.
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Old 11th November 2011, 03:17 PM   #7
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Found JLH. But this looks great. Yet it isn't a chip driver. There appears not to be one even though I've seen them in some products before. A Nady PMX-420 for example. All IDs were ground off though and was using IGBTs as outputs. Sounded better when MOSFETs were swapped.
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Old 12th November 2011, 01:44 PM   #8
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/curses customized Google searches

I was able to find plenty of references to the Shaw and Baxandall articles, but that's it.

Anyway, I've had some fun simulating a quasicomp stage (BC637/638, 4x BD137F, 2x 20V), and it's been an interesting experience so far. Looks like a negative DC offset increases CFP output quiescent current, and if that makes your amplifier unstable into critical capacitive loads, you're in trouble. Yet, with a sine signal crossing the same regions, the simulated circuit never breaks into oscillation. Huh?
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Old 14th November 2011, 07:41 PM   #9
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I'm worried about the same stuff. below +/-50V it seems stable. Above 50V, not so much. At least that's what the sims say. I'll probably have to run the gate resistor to a more negative rail to make sure it can turn off.

I might just do the smart thing and forget class-a/b chip amp and just go discrete with a circuit intended for quasi.
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Old 14th November 2011, 10:18 PM   #10
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Quote:
Originally Posted by davygrvy View Post
I want to experiment with silicon carbide static induction transistors (SiliconSouth SJEP120R063A)..
Oops, meant SemiSouth Laboratories, Inc.
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