Transistors

William Shockley et. al. (1947) after many attempts established two point-contact diodes very close together (~ 0.01 mm apart) on a germanium chip (base). The diodes interacted, making a three pole device with curious properties. The current in one pair (base-emitter) affected the current in the tother pair (base-collector). The classic understatement of all time was added as a rider to the paper "... no commercial applications."

The transistor symbol is a styilized diagram of a three pole point-contact transistor.

A transistor acts as a current amplifier or a switch. In 50 years transistors evolved via PNP and NPN 'sandwich' type stand-alone devices, to become the micro components of integrated circuits, that literally contain millions of transistors per square cm. The descendents of that 1947 point-contact transistor (with "no commercial applications") have changed our world.

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