Thanks very much for that audioguru. I have some follow-ups to that.
I think one of the things that I'm getting confused as I focus on the theory aspect is which variables are what I'd call "choice" variables and which are dependent upon them. I take it that you wanted 10x voltage gain, and 0.4mA current through Rc and then selected other resistor values from there. Is that right?
You mention that "if the collector with no input is 5v then it can swing.....then Rc = 10k and Re = 1k"
That's where I'm getting kind of hung up, I'm not fully understanding how the presence of the transistor is affecting the voltages across the collector and emitter resistors. I seem to remember that voltage gain at the collector is the ratio of Rc to Re, so I can see why you've selected that if you are going that
....but let me make sure I understand the rest of it. You knew you wanted .4mA through the collector, so you divided that by hfe to get the required base current. Then you found what total resistance through the divider would generate 20 times base current, which was about 259k ohms. Then, knowing you had a .65V drop base to emitter, you allocated the resistance between r1 and r2 such that you would achieve the 1.74uA base current you knew you needed for your desired 4mAmps through the collector. For what it's worth, I get (1.15-.65)/226k = 2.12 uAmps. Is this just rounding error, or am I not following it right?