A metal that is used as an electron emitter.
Copper
Iron
Tungsten
Zinc
Tungsten is used as an electron emitter as it has a very high melting point (3655 K) and moderate work function.
Why is Tungsten metal not used as a Thermionic emitter? How is it modified to be a good Thermion emitter?
A transistor is used in common emitter mode as an amplifier. Then: