>> plot_demo
Io =
   1.0000e-04
Vin =
     5
beta =
     2
R =
        1000
press any key to continue
now use the zoom command, and the ginput command to obtain
the intersection values of the two lines
>> print plot_demo_2.ps
>> zoom on
>> zoom off
>> ginput
ans =
    1.7550    0.0032
>> print plot_demo_3.ps
>> diary off