350 



THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1954 



than they really are. For example, as shown in Fig. 15(a), by using an 

 active element a parallel combination of convenient elements such as a 

 0.1 henry inductance and a 10,000 mm/ capacitance can be made to look 

 like the series combination in Fig. 15(b) of difficult or sensitive elements 

 hke a 100 henry inductance and a 10 mm/ capacitance. 



This transformation can be made with the transistor circuit of Fig. 

 15(c) which is also drawn as the equivalent circuit of Fig. 15(d). 



In the circuit of Fig. 15(c) the resistor R^ is adjusted so that the 



\0/Lt/jf 



(a) 



C <fR 



-R'>-[!^ i-C 



,R2RpC 



L 



R2 r\ p 



(e) (f; 



Fig. 15 — Impedance inversion. 



