punch through devices

hi all, can someone plz tell wat are punch through devices and wat is their switchin speed and on state resistance

Jamie wrote in news:eOaXi.670$ snipped-for-privacy@newsfe06.lga:

I'm looking into those now on Google. Best find so far is this:

While I go on with this, there's one question I'm hoping I can get answered faster here: Are TVS's enough like zener diodes that they can be used as simple voltage regulators in the same way, but with the additional fast surge suppression advantages that TVS's are intended for?

A secondary question, related to that: If they are useful as regulators, do they also exist like zeners, with forward voltages as low as a volt or less, so they can give crowbar protection against reverse polarity, in conjunction with a fast fuse, something a standard zener is useful for?

Jamie wrote in news:4AuXi.127$ snipped-for-privacy@newsfe06.lga:

Thankyou. If the curve response is sharp, then flat for a decent range if currents in the low milliamps they might do ok. Any word on forward volts? Only thing I know is it would have to be a unidirectional part, and I guess it would then be a standard silicon 0.6V drop, but I haven't got one to test, and I haven't yet seen a data sheet tell me what their forward voltage is.