SUMK CIRCLJT ASJ'ECTS Ul' TlUi I KWSISIOR 



387 



of Figs. 20 and 21 which give some of the iterative properties of a general 

 fourpole and the effect thereon of an interstage matching transformer. 



The iterative method of course does not exhaust the possibiUties of cas- 

 cade amphfiers. They can also be designed stage by stage. Even when feed- 

 back is large they can be cascaded together in the manner used for filter 

 sections. A particular design of this sort is shown in l-'ig. 22. Tt is a grounded 



CIRCUIT 



EQUIVALENT CIRCUIT -EACH STAGE 







^^ 



Equations: 



rc+ Ra^ Re 



ii(Ra + ri, + i\) + kr, = vq 



hir, - r,J + IARl + >\ + Re- r„,) = 



Circuit delerininant A = {Rq + n + r,){Ri^ -\- r , -V Re - r„) 



> for stability 



Without feed back (r, = 0) 



Iterative impedance Rq = Re — >'m , Rl = fb 



Circuit determinant A = {rb + Re — rnY 



Insertion Power Gain Gi = 



( '- -Y 



\n + Re - r,nj 



Nominal Type A Gain with Re = 36000" 

 without feed back 23'"" 

 with ft normal 21'"' 



Fig. 19 — Synopsis of grounded emitter cascade. 



base Stage followed by a grounded collector and accordingly has the tube 

 analog grounded-grid, cathode follower, from which one would expect that 

 the terminating impedances would be low and the interstage impedance 

 high. This amplifier matched a 600-ohm line to better than 10% and had 16 

 db insertion gain, with a bandwidth of about a megacycle. An adaptation 

 for video purposes was made to obtain over a band from 100 cycles to ,S.5 

 megacycles, an insertion gain of 20 db in a 75-ohm coaxial line. 



