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PREFACE

Electron tube  information  supplied  by  manufacturers  generally  consists
of static characteristic  curves,  maximum  ratings,  and  typical  operating
conditions.  Although  these  data  are  useful,  they  are  inadequate   for
design  work,  as  component  values  that  are  selected  based   on   them,
usually have to be altered in the  actual  circuit  to  achieve  the  desired
performance.  Extensive  use  of  cut-and-try  methods  by  circuit  designers
clearly indicates the need for additional  electrical  information  on  these
tubes,  and  for  modification  of  the  mathematical  methods  for  handling
this  information.  The  triode  curves  given  in  this  Manual  consist  of
standard plate characteristic  curves  with  contours  of  constant  grid-to-
plate transconductance ( g_m ), and contours of constant plate conductance
( g_p ), superimposed on them.

  Curves provided here for tetrode  and  pentode  tubes  have  been designed
to present the rapidly  varying  relations  in  full,  and  reduce  the  more
slowly varying relations to correction curves.  For  this  reason,  the  con-
tours of constant grid bias are plotted  as  a  function  of  screen  voltage
and plate current, rather than as standard plate characteristics.

  In addition, contours  of  constant  grid-to-plate  transconductance ( G_m1 )
are superimposed on the static screen  characteristics.  The  pentode  curves
also include correction curves for X_p and X_c2 as  a  function  of  e_b/E_c2  to
allow adjustment of the design for  any  ratio  of  plate-to-screen  voltage.
This permits the determination of both plate and screen current at  any
value of plate and  screen  voltage.  Tube  data  presented  in  these  forms
are  called  "G-Curves."  G-Curves  permit  design  over  a  wide  range  of
operating  conditions  and  help  in  the  design  of  circuits  which,  when
actually built, conform closely to the predictions of the calculated  design.

  G-Curves contain the dynamic as well  as  the  static  characteristics  of
a tube in  a  single  convenient  graph.  One  of  the  important  advantages
of the G-Curve technique is that the designer  can  meet  specific  require-
ments  by  making,  on  paper,  point-by-point  determinations   of   dynamic
operating conditions anywhere  within  a  tube's  ratings.  It  is  therefore
possible to optimize a  design  so  that  a  given  performance  can  be  ob-
tained  with  minimum  tube  element  dissipation.  Tube  life  and   circuit
 
 
 

                                                                                                             vii
 
 

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