In the late 1940s, William Shockley led a team at Bell Laboratories to develop a new kind of amplifier for the US telephone system. He, together with John Bardeen and Walter Brattain announced the invention of the bipolar “junction transistor” at a press conference on July 4, in 1951. Shockley once explained transistor-amplifiers to a student saying: “If you take a bale of hay and tie it to the tail of a mule and then strike a match and set the bale of hay on fire, and if you then compare the energy expended shortly thereafter by the mule with the energy expended by yourself in the striking of the match, you will understand the concept of amplification.”
When a small input voltage results in a large output voltage, the effect is amplification. A transistor can serve as an amplifier by raising the strength of a weak signal. If a DC bias voltage is applied to what’s called the emitter base junction, the transistor transitions into a forward biased condition. Let’s unpack that statement.
A wide mouthed bass, a big funnel, and a large diameter telescope have one thing in common. They each allow easy entry. This can help the fish to scoop up food, the funnel can be used to rapidly fill a narrow jar, and a big lens on the front of the telescope has a lot of light gathering power. In all three examples, this can also be stated as low input resistance. In the case of a transistor, the low resistance input is called the collector. It is, by design, a way to gather as many electrons as possible from a relatively weak source.