The Transistor as a Network Element

It has become customary through the years to classify linear circuits as either active or passive. This convenient, but arbitrary, division has encouraged a philosophy that regards each as a separate and distinct domain. The recent spectacular advances in active devices suggest that in some cases the traditional boundaries should be erased and that a unified approach should be made. In particular the development of the transistor offers the possibility of interspersing small active elements throughout a passive network to achieve certain desirable effects. This paper intends to survey a few of the ways in which a transistor can be used to advantage in transmission networks. The discussion is divided into four parts as follows: 1. Reduction of dissipation. 2. Elimination of inductance. 3. Production of delay. 4. Inversion of impedance. * Presented in part at the Radio Fall Meeting, Toronto, Ontario, Oct. 28, 1953. 329 330 THE BELL SYSTEM TECHNICAL J O U R N A L , MARCH 1 9 5 4 The first portion offers a new approach to the everpresent problem of imperfect reactive elements. The second portion discusses a method of combining resistance and capacitance with transistors to produce characteristics conventionally realized by inductance and capacitance. The third portion proposes a technique for obtaining any specified delay characteristic with a two terminal active structure. The fourth portion considers means of using a transistor to transform passive elements of ordinary size into passive elements of greatly reduced size.