THEORY OF NEGATIVE IMPEDANCE CONVERTER 



99 



tioned, consider the practical design of the El converter. Here the ratio 

 — (ni — 1)/(m2 + 1) to 1 is —0.9: 1 over most of the voice frequency range. 

 This is not the over-all ratio of transformation of the device, but only the 

 ratio of the ideal converter C, Fig. 6(b). The ratio of transformer T and 

 the effect of the other circuit elements must be considered in determining 

 the over-all effect of the converter from terminals 1 and 2 to terminals 3 

 and 4. The transformer ratio is 1:9 from terminals 1 and 2 to the tube 



'? Ri L R ?"* 



EQUIVALENT 

 CIRCUIT 



OF 

 TRANS- 

 FORMER 



1+//2 



Fig. 6 — The El converter circuit. 



cathodes. The shunt arms of the networks on both sides of the ideal con- 

 verter C are relatively high compared to the impedances between which 

 this converter has been designed to operate at voice frequencies. Therefore, 

 these shunt arms can be disregarded at voice frequencies although at fre- 

 quencies above and below the voice band these shunt arms represent a 

 problem for the circuit designer from the viewpoint of stability. In the 

 actual El circuit the series arms such as 2Rp/{l + fi2) and 2i?2 could be 

 ^xancelled out by adding in series on the right-hand side of the ideal con- 



b 



