THE DESIGN OF TETRODE TRANSISTOR AMPLIFIERS 



825 



loci of constant real and imaginary parts of Y2 become the mutually 

 orthogonal circles shown in Fig. 8. Thus the value of L + jM is deter- 

 mined by the load admittance and two-port parameters. 



Contours representing constant input power, with equal increments 

 of power between successive contours, are always parallel equally-spaced 

 lines in the L-M plane. However, as may be seen from (19) and Fig. 6 

 different cases have different directions for the line normal to the con- 

 tours, (the gradient line) and also different power increments for a given 

 spacing of equal-power-input contours. It is convenient to define a new 

 \ariable A^ which is the component along the gradient line of the vector 

 starting at L = 1, M = and going to L, M. Thus 



Pi = P.o(l + CX) 



(27) 



Equation 27 suggests Fig. 9(a) which shows loci of constant power input 

 plotted as a function of X. If Fig. 9(a) is shown on a transparent ma- 



90 





1.8 



1.6 



1.4 



1.2 



1.0 



0.8 



0.6 



0.4 



0.2 



0.2 



0.4 



0.6 



0.8 



1.0 



1.2 



1.4 



1.6 



h,ah 



2"21 



2h 



22r 



^(L.jM) 

 ^n22r 



R,+jx, 



1.8 



Fig. 9(b) — Input impedance as a function of L and M. 



