Development of Electronics - II

The rapid advances after that are due largely to the introduction and progress of the vacuum tube as an amplifier for electric signals. Dr. Lee DeForest, with his audion tube, invented in 1906, was a leader in this field. As the design of vacuum tubes advanced, radio broadcasting progressed rapidly. Regularly scheduled programs were broadcast in 1920 by station KDKA in the standard amplitude modulation (AM) radio band. The commercial frequency modulation (FM) radio broadcast service was started in 1939. Stereo broadcasting in this band began in 1961.

Commercial television broadcasting was started officially in 1941, but its popular use did not begin until 1945. Our present color television system was adopted in 1953.

Since the invention of transistors in 1948 at Bell Telephone Laboratories, solid-state devices have replaced tubes for most uses in electronics, radio, and television. The transistor is an application of controlled electron flow in solid semiconductor materials such as silicon (Si) and Germanium (Ge). Transistors and tubes have similar uses for the control of electron flow and amplification of signals. The transistor is much smaller, however, and more efficient, as it does not have the heater used in tubes.

Solid-state electronic devices include transistors, diodes, and integrated circuits. A diode is not amplifier but is used as a one-way conductor to convert alternating current to direct current. Solid-state devices have made new application practicable because of their small size and the economy of ICs packages. One example is the rapid growth of digital electronics for electronic calculators, personal computers, and many other uses.