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can the Mosfet be turned on as shown on picture? My desire is voltage on M1 fire the SCR stay on forever.

V2 is ramp voltage.

enter image description here

  • What is ramp voltage? What does your simulation show? – winny Jun 02 '19 at 18:55
  • V2 rises linearly from 0 to 10V and then stays constant at 10V. My expect is when V2 reach about 6V, the SCR starts to conduct. I do not have simulation. –  Jun 02 '19 at 18:58
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    why is the mosfet even needed? it serves no function and it will just fry if it ever turns on. not to mention it reverse conducts (and fries) as long as v2 < 5V – DKNguyen Jun 02 '19 at 19:54
  • Look at diacs and how they are used to trigger SCRs Theoretically you could just use a diac with the appropriate breakdown voltage alone but they only come in lower power and have some other issues. If you use both you can also tune the trigger voltage with resistors – DKNguyen Jun 02 '19 at 20:22
  • BTW, your simulation failed because you're missing a .lib or .sub file (at least, it's not shown in your screen shot). When selecting the SCR, its description says: Generic SCR symbol for use with a model that you supply. Check this – Huisman Jun 02 '19 at 20:47
  • Show that instead. “ramp voltage” is vague and we do not like that here. The elephant in the room is the SCR-MOS combo non the less. – winny Jun 02 '19 at 21:03

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