I found this Vgs-Vds graph from the this youtube video and I had not seen this kind of graph before for MOSFETS. neither in other sources nor in the few mosfet datasheets I checked out.

It makes sense to me that as Vgs increases Vds will decrease as the "switch closes".

However, the saturation region is shown in the middle and the linear region is showin at the right side. I found this... odd... Could anyone provide some intuition on why is this the case?

In the graph:

  • Vdd is the voltage of the power source.
  • Vt is the threshold voltage

enter image description here

enter image description here

  • \$\begingroup\$ What is odd in the saturation region? \$\endgroup\$
    – G36
    Jun 8, 2021 at 20:10
  • \$\begingroup\$ It's a bit unconventional and it's not clear what drain current is but, it makes sense if you assume drain current is somewhat constant. Just use the graphs in data sheets because they give you more information and in a standard way. \$\endgroup\$
    – Andy aka
    Jun 8, 2021 at 20:11
  • \$\begingroup\$ @G36 I find it hard to understand why the marked regions are indeed the saturation and linear regions and not the other way around. \$\endgroup\$ Jun 8, 2021 at 20:13
  • \$\begingroup\$ I see, here you can find the answer electronics.stackexchange.com/questions/129408/… \$\endgroup\$
    – G36
    Jun 8, 2021 at 20:19
  • \$\begingroup\$ When Vgs starts to exceed Vt, the gate capacitance makes an abrupt rise in charge C=Q/V to be in the saturation region. Whereas BJT capacitance rises in saturation when the reverse CB voltage goes to 0 and then is fully saturated when Vbc approaches but never reaches Vbe resulting in low mV drop per mA across Vce or Rce. Diodes reduce in capacitance when BC voltage is more reversed and thus Vce is out of saturation. So the confusing name has more to do with charge saturation zone changes and of course is confusing but affects recovery time in switches. \$\endgroup\$ Jun 8, 2021 at 20:33


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