This may be more of a physics question than a support one, but I appreciate whatever info is offered.
Since the discrete transistors are hundreds (thousands?) of times larger than the tiny transistors that are etched (printed?) in silicon on an IC, shouldn't the kit versions of these circuits be able to handle vastly more current than the IC ones? After all, a through-hole resistor can handle more current than a surface mount one. Power dissipation in resistors seems to correlate closely with physical size, and I believe that's true for capacitors, inductors, and diodes? But as far as I can tell, these kits have similar current ratings to the classic ICs they're modeled after. I'm sure that's intentional, but I'm curious if its relatively easy to modify these kits so they can handle much more current. For example, if I replaced the 3904 & 3906s with 2222 and 2907 transistors would the 555 and 741 now handle 800ma? For that matter, would using ZTX968s & 1049s let it handle 4 amps (assuming the resistors and PCB traces were large enough)?
Those three transistor families all come in TO-92 packages, so I guess I'm also don't understand why they have such different capabilities either. Is the size of the PN and NP junctions in the ZTX968 16 times larger than in the 3904? I know that most higher power transistors come in physically larger packages (TO-220 etc), but is that just to allow a larger heat sink surface area, or are the silicon boundaries physically larger? And for the ones that do come in the same package size, is there an advantage to the lower ones other than cost? Is it cheaper to make a 3904 than a 2222, or can the 3904 switch faster because it's smaller?
I know that's a lot of questions for one post and that this isn't an electronics classroom. But again, I appreciate any insight.