Need help with SCR (Silicon Controlled Rectifier)

[sushawn]

Hello electronics gurus of the CPF world! A LOOOOOONG time ago (in fact, I was about 15 years old), I first learned about SCR’s… Silicon Controlled Rectifiers, if memory serves. As I recall, they could be used sort of like a solid state relay, plus could be made to latch in the “on” state. In other words, I could connect one inline with a circuit, and it would act like an open switch until a momentary current was applied to its “gate” (my word, not necessarily the technical name of it), at which point the SCR became like a “closed” switch. Now here’s the interesting part: once in the “closed” state it didn’t matter if the current on the gate was removed, the SCR would remain “closed.” I read a lot of examples of Silicon Controlled Rectifiers circuits, but I am still confused.

Am I describing this part accurately, or do I have it confused with something else? I know such a component exists, but am hoping someone could explain it to me.

I’d also like to understand some basic properties for such a part…

Does it drop a voltage across it like a diode does?

Does a small amount of current “leak” even when in the “open” state?

Will it truly remain “closed” forever once tripped, so it could keep running a load for hours, days, weeks, or even months… or would it eventually “open” itself again?

Is there a significant heat buildup through this part?

Thanks in advance to whoever helps me understand all this! I appreciate your patience in dealing with such a dim electrical engineering wannabe as me. /ubbthreads/images/graemlins/blush.gif