THE TRANSISTOR AS A NETWORK ELEMENT 



333 



^A\ '■^'0"^ 1 f- 



,f L, ' C 



— nm^ vw- 



c, L, x^ 



(a) CONVENTIONAL 



njw^^V-^^^ 



(b) ACTIVE 

 Fig. 2 — Confluent band filters, (a) Conventional, (b) Active. 



rai.siug the impedance of the shunt !)ran('h without changing the im- 

 pedance level at the input and output terminals. At the same time the 

 elements assume much more reasonable values. The modified configura- 

 tion together with the active portion is shown in Fig. 2(b). 



I'sing the filter described above, a series of transmission curves were 

 calculated and are shown in Fig. 3. When ideal elements are assumed, 

 the transmission is 



e = 



kV 



'here A" = 



ip' + kp-{-l) [p4 + kp' + (fc2 + 2) p2 + /cp + 1] 



Wi 



and 



P = JO} 



Calculation of this expression results in the classical characteristic 

 labeled "Ideal Passive". When, however, typical \'alues of element re- 

 sistance are introduced, the transmission is 



e = 



(ao + «ip + a-ip- -\- azp^ + aip^Y — {hp -f 52^"^)^ 



