Transistors - I think it very remarkable how transistors suddenly appeared on the scene, and how in a relatively short space of time developed into the devices we have today.
The word transistori is made up from two words – transfer and resistori. First and foremost from outward appearances it has three legs, and these three legs have names, their names are; Collectori, Base and Emitter.
A small current in the base of the transistor controls a large current in the collector this gives us a device that can amplify signals, or can switch larger currents by the application of a small current in the base.
GAIN can be found by dividing the collector current by the base current and can be anything from a figure of 30 to 800