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Fig 2-1.  Voltage relations of triode and pentode amplifiers.

                Small signal  components

                       e_p     i_p
                       e_g

                Instantaneous components

                       e_b     i_b
                       e_c

               ( See General Symbols page xi.)

               In the case of pentodes the plate conductance is normally negligible  -
that  is,  plate resistance r_p  is  very  large  provided  plate voltage e_b  is more
than  half  the  screen  voltage,  E_c2.    The  pentode  amplification  equation
for  constant  screen voltage  follows  from Equation 5  by  setting  g_p  equal
to zero, and by replacing gm with g_m1.  The resulting equation is:

                                   K =  e_p/e_g1  = -g_m1* R_L                      (6)
 

   As the transconductance is dependent on  both  G_m1 and  X_p ( see equation 1 ),
equation 6 reduces to:

                                      K = -G_m1* X_p* R_L                             (7)

                                                                                                                    7

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Copyright 2008 for Phyllis K. Pullen, M.D.,
by Robert J. Legg