108 



BELL SYSTEM TECHNICAL JOURNAL 



matched transformer. The resultant circuit is that for a pentode output 

 transformer in each case, where the plate resistance of the tube is so high 

 compared to circuit impedance that we can consider it to be a constant 

 current generator of g^Eg amperes, where gm is the grid-plate transconduct- 

 ance and Eg the grid signal voltage. Thus in this case the mis-matched 

 transformer also gives 6 db more gain than the matched transformer. 



(3) Interstage Transformer — If the voltage generators of Figs. 1 and 4 

 are replaced by their equivalent current generators gmEg = Ei/Ri and 

 g^E'g = E[/R[, then (31) becomes. 



^2 



= 4 



R1C2 

 RiC^ 



2 E 



The first relation in (26) may be substituted in (32) giving, 



Ci C2 gm Eg 



£2 



Cl C2 gm Eg 



(32) 



i.3i) 



Thus, in the interstage case, this mismatched transformer has only 3 

 db more gain than the matched transformer. 



Here, as in the case of the first mismatched transformer discussed in this 

 paper, there is an increased sensitivity to capacity variations. In practice 

 it appears that this is not always serious in wide-band intermediate-fre- 

 quency amplifiers. Some improvement in noise figure and power handling 

 may be obtained, as before, without encountering difficulties with double- 

 peaked pass-band characteristics. 



The design formulas given in this paper have been used successfully in the 

 design of experimental intermediate frequency amplifiers in the 65 mc region 

 having band widths of the order of 10 to 20 mc. 



