hi agu,
How can DC not be a signal.?
After all DC stands for Direct Current and AC stands for Alternating current, the only difference I know of between the two ie: DC and AC
is that direct current does not change its direction of flow with time whereas alternating current does change direction of flow with respect to time...
So from my understanding, both DC and AC are both in effect signals.?
I guess that your interpretation of the DC and AC states is based on its usage in some semiconductor datasheets.
I would agree with Carl, there is some confusion of the definitions of hFE , hfe and DC [saturation states].
It seems to depend upon which datasheet or data source you take as the reference.
All transistor datasheets that I have seen call hFE "DC Current Gain".
All transistor datasheets that I have seen show hfe at 1kHz (small signal current gain). Fairchild's datasheets show the hfe dropping as the signal frequency approaches the gain-bandwidth product.