826 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1956 



terial, its center (at X = along the gradient line) can be superposed 

 with the point L = 1, ilf = of Fig. 8. With the gradient line of Fig. 

 9(a) oriented at the argument of —hnh^i , or S in the L-M plane, one can 

 easily determine graphically the power gain at any point in the L-M 

 plane compared to the power gain at 1, 0. With Fig. 9(a) superposed on 

 Fig. 8 as just described the viewer gets a bird's-eye-impression of tlic 

 paraboloid of power output and the inclined plane of power input simul- 

 taneously. With such a bird's-eye view, it is easy to assess possibilities 

 for power gain with all possible angles of load termination. 



The evaluation in input impedance is done through use of (16) from 

 which is obtained 



^ = Z,. = hn + (L + jM) t^^ 



or 



Zin = hn + (L +jM)(e-n 



hnh 



21 



Zhf22r 



(28) 



(29) 



For evaluating the second component of (29), it is convenient to have 

 a second transparent overlay, Fig. 9(b), consisting of a rectangular grid 

 to the same scale as the L-M plane. Fig. 8, with coordinates marked as 



(Zin — hn) Ri 



and 



This overlay is placed over the L-M plane with the 



^1 



hioh 



12fl'21 



2ihj22r 



axis making the angle d with respect to the L axis. Thus on the rec- 

 tangular overlay for any point in the L-M plane, one reads 



Zin — /ill 



hiih 



■21 



2/?.,. 



r.\i;TI('UL.\U DESIGNS OF TETKODE TRANSISTOR AMPLIFIERS 



IMie charts and optimum rc^lationships developed in the preceding 

 section are convenient starting points in the design of amplifiers. They 



