As you may know I'm steadily working my way through this book by Lorne MacDonald and I like it because it has not only lots of problems but each chapter has actual breadboard exercises :tu:
Anyhow I have arrived at this chapter
IMG_20250728_185826902 (1) (1).jpg
So that's cool except for the mind numbing included parts about Q point, maximum voltage swing, input impedance....and dude...yeah alpha crowding :loco
I'm wondering now in amplifiers when voltage gain is used vs current gain or vice versa. Or both.
I'm sure this will be revealed. 8|
This should be simple because hey don't transistors amplify current (Beta, Hfe) :grr
Still I remember scoping the input and output of my old dukane amp and seeing how much larger the output was...in volts Vpp :grr
Ok wait a minute....if we put more current through a resistor guess what we get :trouble
I'm gonna have to order some coffee ☕ from Argentina :dbtu:
That´s the point.
Tubes also control current output, in this case depending on grid voltage.
That´s why both use a load resistor, as you noticed current develops a voltage across a resistor.
In very general terms, the pre-amp does the voltage gain (to boost the tiny signal from pickup or microphone, and the power amp does the current gain (required to drive a speaker).