I have a problem , how to explain a certain graph....

i have a circuit of an NPN CC BJT with PNP diode-active load ... and the graph came from o V- 0.7V not a straight line its curved like and exponential graph . then after this region both Vin and Vout are linear (ie straight line is obtained ) ... can someone please explain how this graph is obtained , and which part is the active region and cutoff region.???

thanks
elly

 

I have a problem , how to explain a certain graph....

i have a circuit of an NPN CC BJT with PNP diode-active load ... and the graph came from o V- 0.7V not a straight line its curved like and exponential graph . then after this region both Vin and Vout are linear (ie straight line is obtained ) ... can someone please explain how this graph is obtained , and which part is the active region and cutoff region.???

thanks
elly

You need to post the schematic and the graph.

 

i attached the graph and the schematic ..
thanks

 

Is the horizontal axis a sweep of V1?

 

it is Vin against Vout .. Vin = (Vdc = 1.85)