Hello,

looking at the BT151S datasheet: www.nxp.com/documents/data_sheet/BT151S_SE=
R_L_R.pdf

There are some parameters that I don't understand.

The most important is the latching current. Is it the current necessary to =
trigger the
device (via anode/cathode, not gate) in case the breakdown voltage is reach=
ed?
This sounds logical to me, but when I read that Vd=3D12V then we're really =
far away from
breakdown.. so I think the above theory cannot be true anymore. :-/

This latching current parameter that I'm not sure I understand seems relate=
d to another
parameter, the holding current, which I imagine being the current that must=
 flow between
the anode and cathode to keep the previously triggered device latched, when=
 the gate stops
being triggered. Or, in other words, the holding current is the limit BELOW=
 which the
anode/cathode must go for us to "free", unlatch the device.

Another question if You don't mind.. SCR's are harder to trigger via the ga=
te (i.e. they
require more current) when the tension between anode and cathode is lower, =
right? I.e. if
it's near breakdown, then the gate will become more sensitive, right? Of co=
urse I'm not
going to use it out of specs, it's just curiosity to understand more the in=
ner workings
of the device (that is roughly equivalent to a PNP+NPN transistors, arrange=
d to cause
self-latching).

Please could You shed some light on this latching current parameter meaning=
? Thanks!

With kind regards,
Cesare - TechInfoService

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