So long as the transistor is properly DC-biased, the AC behavior of
an amplifier like the ones we considered today does not depend on the specific value of . When we make the AC equivalent,
is treated as if it is at ground, so the value doesn't matter.
However, note that the value of does matter for proper
DC-biasing of the transistor. It must have a value such that the
voltage through the base resistor voltage divider at the transistor base is large
enough to keep the transistor ``on'' (i.e., in the linear active
regime) throughout the entire input voltage swing.