The Transistor

Figure 45. An amplifier circuit and an oscillator circuit using a transistor. (Adapted from Reference 45.)

This will be recognized as a "double crystal detector." The transistor, however, is used as an amplifier.^47,48 A very feeble input current through one contact can control a much larger current from a source connected to the second set of contacts. Preliminary tests have resulted in amplifications of 100, and currents up to 10 megacycles have been used. This device was developed by Bell Telephone Laboratories. The extent to which the transistor may replace the vacuum-tube amplifier is not yet generally known (1949). The input impedance of an experimental transistor is about 1000 ohms, and the output impedance about 10,000 ohms. The power handling capability is 50 milliwatts, and the power consumption about 0.1 watt. Circuits for using the transistor as an amplifier and as an oscillator are shown in Fig. 45. A coaxial transistor, with electrodes on opposite sides of a thin germanium element, has been announced.⁴⁹