In contrast to devolution, I hope, my forum-member friend. I began with idea of taking two N-channel MOSFETs and, using LTspice, coming up with the simplest, most effective discreet component circuit that could drive those two power transistors in class D mode. All because I was a bit bored.
It turns out that Bruno zeroed in on the solution quite well, not surprisingly. It befits his genius, I'd say.
I tried all kinds of configurations including a class AB voltage amplifier stage that I used in my last class D design--an even simpler circuit that was a modified complementary class AB type. I guess I will try to show an image of it as well as the dual N MOSFET circuit that I now think merits my "N-champ" moniker. I know that this circuit isn't completely optimized. I might do more of that later, if I feel it worthwhile to me. I plan to upload one or more images later.
I had intended to take that class AB driver stage and instead of driving one N and one P-channel MOSFET in source follower configuration, drive one N-channel in direct source-follower mode and another by using a PNP transistor in a modified Sziklai pairing. That approach was not fulfilling my desire for simplicity or effectiveness. The Lower MOSFET in the totem pole tends to suffer from switching speed limitations, for one thing.
The circuit was still not decent-looking enough with the
standard differential pair that level-shifted the signal to the upper MOSFET and also fed it to the lower one. I could not get the propagation delay of the stage lower than about 40nS. In class D, PD translates almost directly into distortion. It is a hideous type, too. I remember my first class D project 25 years ago suffering from it in a very severe way. In really bad cases it sounds like severe crossover distortion that might plague class AB.
The problem was the pull-down resistors for the long tail pair driving the differential amplifier/level shifter. They suck away the drive for differential pair and are slow. I guess that is why the current mirror was invented. I just basically ended up with a cross-linked CM.
As another of my member-here friends recalls, I was not far from the original UCD concept several years ago, before I knew of the existence of Bruno's concept.
Enough apparent horn-tooting. I really just want to show enthusiasm, but the personal background information seems to be an unfortunate aspect of expressing satisfaction and airing that dung out right away and getting it out of my system, so to speak. It's probably mostly self-delusion, anyway, since I know what my IQ is. It is almost a curse for it to be too high at times, sadly.
. Too high mine is not, in my opinion. I really want a world society based on cooperation instead of competition (predation).
I definitely agree that we build upon the work of those before us. Besides, I would be much surprised that given the opportunity, I will be able to get the circuit to work in real life. It won't help that I intend to use P2P wiring on this thing if I do try. I might just stay in the realm of simulations on this project, and possibly advisedly so.
There you have it, the good and the bad. Thanks everybody for being forbearing peers as you have been. I invite comment, but being non-prolific at writing, my responses will probably be pretty anemic, if at all. It much depends on what comments there would be.
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