biasing voltages, on the other hand, are derived from current conducting through the tube. The most
common types of self-biasing are cathode biasing and grid-leak biasing.
The CLASS OF OPERATION OF AN AMPLIFIER is determined by the bias applied to a triode.
An amplifier operating as class A conducts continually through the duration of the input cycle. Class AB
operation occurs when the amplifier conducts for more than half but less than the entire duration of the
input cycle. A class B amplifier conducts for only 50% of the input cycle. The class C amplifier conducts
for less than half of the input cycle.
TRANSIT TIME is the time required for electrons emitted by the cathode to reach the plate.
Because transit time in a vacuum tube is considerably less than the speed of light, vacuum tube operation
is affected at high frequencies.
INTERELECTRODE CAPACITANCE is created by the naturally occurring capacitance between
elements in a vacuum tube. One effect of interelectrode capacitance is to feed back a portion of the output