Fet for turning on high voltage.

[Ioannis]

Hi Henrik.

You are right about the power mosfet, but the schematic was ready from another project. I mentioned that, so one can of course select a lower amp one.

I just needed the low Rds for my project. P-Mosfets with low Rds, are hard to find.

The idea of optocoupler is great! Vishay SFH619A is 125mA capable and sure there must be stronger devices.

Ioannis

[jmgelba]

Thanks for the responses guys. Good stuff. This is what I tried in simulation and it works. The NFET used will be a STN3NF06.

[HenrikOlsson]

Hi,
If I'm looking at the correct datasheet the SI4401 P-channel MOSFET has an absoulte maximum Vgs rating +-/20V. If wired as in your schematic the MOSFET will see 24V (or 45V if that's the supply voltage) between the gate and the source which is above its rating - in real life it will likely self destruct even though it doesn't in the virtual world.

You need a second resistor between the gate and the collector to form a voltage divider as in Ioannis schematic.

/Henrik.

[jmgelba]

Henrik, Im not using the SI4401 in the schematic, it was a random device picked from a list of available parts.