I know that Q-point is intersection of AC load line and DC load line.

but!
I don't know why DC load line is different from AC load line.

I think that it means difference of resistance value.

WHY???????????

Help me~

 

It is not the resistance, but the AC impedance which is frequency dependent.

 

To echo what papabravo has stated, a device that exhibits an ac load-line in addition to a dc load-line possesses a load impedance that is not purely resistive.

hgmjr