THE TRANSISTOR AS A NI<7rW<)RK ELEMENT 



335 



becauHe at midfreqiiency the reactive component l)ecome.s zeio in each 

 brancli of the filter. 



Transmission of Synunetrical Tec 



The insertion loss of a symmetrical tee section with p()si1i\'e resistance 

 is a well known concept. It is doubtful, h()we\-cr, if the l)eha\'ior of a tee 

 with a negatix'e t>lement is e(|ually well known. Consider the section 

 shown in Fig. 4 operating between tei'minations R and ha\'ing series 

 arms, A',i and a shunt arm, Rn . Normalize by letting a = Ra/R and 6 = 

 Rn/R- Ins(>rtion loss is plotted vs. I> with a as the third parameter. For 

 b positive the usual loss pattern results; for 6 negative, a more complex 

 situation de\'elops. When b is very large and negative, the section is still 

 producing a small loss, but as b l)ecomes smaller in magnitude the loss 

 drops to zero and finally becomes a gain. There is a lower limit on the 

 magnitude of 6 beyond which oscillations will occur. This limit is reached 

 when 26 = -(a + 1). 



9.6 9.7 9.8 9.9 10.0 10.1 10.2 10.3 10.4 

 FREQUENCY IN KILOCYCLES PER SECOND 



P'ig. 3 — Transmission of confluent band filters. 



