transistor and diode blocking voltages

Depends which way round they are connected and whether they are P or N type!

Hardy

Diodes block reversed voltage due to the way in which the conduct electricty causing a break in the conductive path when they are reversed in relation to the voltage.

transistors can be used in combination with other electronic parts to regulate or block over voltage but how they work is more complicated.

MOSFETs (a type of transistor) can also be used like a diode to protect against backwards voltage.

Further questions of this nature are bast asked in sci.electronics.basics

Bye. Jasen