ABSTRACT
Consider a generic electron device as represented in Fig. 26.1. It consists of three electrodes encompassing a charge
transport region
. The transport region is capable of supporting charge flow (electrons as shown in the figure) between an
emitting electrode
and a
collecting electrode
. A third electrode, called the
control electrode
, is used to establish the electron concentration within the transport region. Placing a
control charge
, Q
, on the control electrode establishes a
controlled charge
, denoted as –Q, in the transport region. The operation of active devices depends on the
charge control principle
:
Each charge placed upon the control electrode can at most introduce an equal and opposite charge in the transport region between the emitting and collecting electrode.