ВЭФ 12 (Astrad VEF 12 Project) - including a transistor tutorial

[ppppenguin]

I think most of us would know about cathode bypass capacitors. What's more subtle is why you get negative feedback without that capacitor.

The question about the pentode is also trivial though we need to make an assumption about the grid voltage because you haven't specified it. We'll assume the grid voltage is zero.

Hence the cathode must be at +3V. Cathode current is anode current + srceen current = 9+2 = 11mA. By ohms law the cathode resistor is 3V/11mA, approx 270R. It will disspate 3V x 11mA = 33mW, hence even the smallest of resistors will suffice.