LME49830 like driver chip for Quasi-Complimentary?

[davygrvy]

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?

[davygrvy]

Topology-wise it can't this simple as adding Q4, is it? MOSFETs being used in place of a pair of SiTs

[palstanturhin]

I do not know anything about electronics, but I think you could make that even simpler...



Just an idea... May not work. More intelligent people shall comment.

[AndrewT]

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.

[davygrvy]

Originally Posted by AndrewT

Read up on quasi complementary.

That's the trouble, I got nothing 'cept for a Dynaco 120A schematic

[AndrewT]

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.

[davygrvy]

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.

[sgrossklass]

/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?

[davygrvy]

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.

[davygrvy]

Originally Posted by davygrvy

I want to experiment with silicon carbide static induction transistors (SiliconSouth SJEP120R063A)..

Oops, meant SemiSouth Laboratories, Inc.