Hi audioguru,
Since when and why does it take so many years to learn how a simple transistor circuit works...
Please recall, the original question was absolutely theoretical about selecting components for designing a circuit, not just selecting transistors. I cannot find any trace of a "simple transistor circuit" in the original question. Transistors were brought up later just "for instance".
A 2N3904 or BC548 as an NPN, or 2N3906 or BC578 as a PNP will work in about 85% of transistor circuits and a 2N3055 or MJ2955 power transistor will work in most of the remainder. Designing a simple circuit for a FET or Mosfet transistor will take only a few more minutes of study.
Now, somebody should really talk to those stupid component manufacturers, too. They just do not stop investing in the production of hundreds if not thousands of different transistor types.
Indeed, even selecting a transistor can get tough...
What if Kate had the following problem (audio example to favor audioguru):
In the large signal voltage amplifier stage of a discrete transistor class AB audio amplifier, I want to know which transistor types are likely to send the whole circuit into oscillation and which are not.
Suppose you already have the whole schematic of the amplifier! The hard part is all done! It's just the type of one transistor missing. How simple the question: Will the amplifier work fine or oscillate with different transistor types in that position? Alas, no sample of the amplifier, no transistor samples either for tweaking (just data sheets in piles), so you need to solve it all in theory and come up with the results for Kate. What if she can't get a sleep until she knows for sure!
Open loop characteristics, loop gain, closed loop characteristics, Miller capacitance, pole-zero image, phase margin, Bode-plots, which stage determines the second pole frequency and to where is it shifted ...
The clock's ticking. Would you go explain it in a few minutes for someone without electronics education?
Hey, when selecting a transistor is so easy, why am I wasting my time. I better quit this forum and never return.
Happy Cristmas for all