Electronics specs questions

MTN-KAT met at pine.cse.nau.edu
Fri Nov 4 15:48:37 GMT 1994


I don't know diddly about electronics. I'm sitting here looking thru a Digikey
catalog trying to figure out which mosfet power transistors and which 
opto-isolators to use for my project.
the mosfets list BVdss, Ip, Idm, Vgs, Rds and PD. From my reading in
Practical transistors and Linear IC's book, BVdss is the voltage to trigger 
the transistor. All of these mosfets are 60V-120V, obviously I'm only running
13.5V max, what am I missing?

The opto-isolators list BVCEO(min), the smallest is a 7V with a current
transfer ratio of 250%, no specs for on/off time. From my reading a darlington
output should boost the current, the catalog doesn't say how much.
The isolation voltage is only 3000V for this particular item, some list 5300V
would they be better for isolating the engine noise from the electronics?

I had ordered some logic level opto-isolators and they came with schmitt trigger
outputs, I tried to run these at slow speed 0.1 sec and they just stayed in on
mode, the data rate is supposed to be 1.0MHz. Could I have been hooking them up
wrong?

Is there a cross-reference manual available, I have a listing for some logic
level IGBT's, HGTP15N40C1 but Digikey doesn't have any part numbers similar to
this. The MOSFETs have a part number, IRF540, once again no similar numbers in
the catalog.

Could someone help me figure out what I'm missing?

Millam



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