enter image description here

As per the diagram:

v-I characteristics of SCR is a graph of anode current I A on y-axis & anode to cathode Voltage plotted on x-axis v-I characteristics can be split into two parts namely Forward Characteristics & Reverse Characteristics.

Now why does the Vak suddenly drops to Vh during conduction... This is unlike a diode where the voltage remains constant even after avalanche breakdown...

Please can anyone explain this isusue to me!

  • 2
    \$\begingroup\$ It's unlike a diode, because it is a thyristor. \$\endgroup\$ Oct 18, 2018 at 13:01
  • \$\begingroup\$ @Marko give me some scientific support to your answer ... And even I know that it is a thyristor and not a diode but diagram is such... \$\endgroup\$ Oct 18, 2018 at 13:08
  • 1
    \$\begingroup\$ There is feedback happening internal to the SCR, that's why it latches. electronics.stackexchange.com/questions/344321/… \$\endgroup\$
    – sstobbe
    Oct 18, 2018 at 13:45

1 Answer 1


An SCR is not the same as a diode, the foldback indicates that there is voltage that the SCR will start conducting, without specifically applying gate current (which is normally the way you would use it). It in effect an avalanche affect.

For a nice explanation (sorry for the fragmented link on the original, google seems to have it right):


  • \$\begingroup\$ The link is not complete \$\endgroup\$ Oct 18, 2018 at 13:18
  • \$\begingroup\$ sorry about that, should be corrected now. Not sure why the first one didn't copy over. \$\endgroup\$
    – user201365
    Oct 18, 2018 at 13:24
  • \$\begingroup\$ BTW it is still a pdf so depending on your browser settings it may just silently download. \$\endgroup\$
    – user201365
    Oct 18, 2018 at 13:31

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