I am learning about thermionic emission and how it led to the vacuum tube. It is said that thermionic emission was a way to increase the flow of electrons from a signal (e.g. in a radio receiving a weak signal, boosted by thermionic emission). What I don't understand is how it "generates" electricity; even if the coil is heated to it's work threshold, wouldn't a coil only be able to emit as many electrons as are supplied?
Thank you for your time