Integrated Circuits

Abstract

Figure 11.1 shows the development of active electronic amplifying devices from the large-size vacuum tubes to integrated circuits. Number (1) is a 6L6GA vacuum tube that has been used as a power amplifier in radio receivers. They were often used in push-pull circuits in power amplifiers such as those in public address systems. Number (2) is a 12SF7 vacuum tube that included both a diode and a triode in the device. The diode could be used to detect the audio signal in an AM radio receiver and the triode as a class A amplifier to amplify the detected audio frequency. Number (3) is a 6HQ5 triode vacuum tube that was designed to be used as a VHF amplifier in color television receivers. The first number in a label for a vacuum tube, e.g., 6 or 12 indicates the voltage that is needed to heat the filament. The last number, e.g., 5, 6, or 7, was originally used to designate the number of electrodes or elements in the device, but this idea was not always used.