The Control of Frequency Response and Stability of Point-Contact Transistors

The frequency response and stability of point-contact transistors are determined to a large degree by control of the point-contact spacing and germanium resistivity. Stability is particularly important in amplifiers in which the impedances of the emitter and collector circuits are very small in the frequency range in which the transistor is designed to operate. Satisfactory stability has been obtained with developmental transistors having a frequency cutoff (3-db drop in the current amplification factor, alpha) ranging from 10 to 30 mc. These transistors operate under approximately the same dc bias conditions used with lower-frequency transistors, and have an average power gain of approximately 20 db. By means of the methods outlined, transistors which oscillate at frequencies as high as 300 mc have been made.