M
Michael
- Jan 1, 1970
- 0
Hi there - I'm working on finalizing component selectrion for a high
side switching circuit (as discussed here a month or so back). I was
recommended the FOD617 optocoupler, but I'd like to find a similar if
not better surface mount part.
I'm looking at using a darlington optocoupler. I think the Sharp
PC452J00000F looks nice, with a 1000% current transfer ratio at 1ma.
The datasheet for the part mentions a VCE saturation voltage (http://
document.sharpsma.com/files/pc452_eJ.pdf, figure 8) of about 1V. What
does a saturation voltage even mean with a phototransistor? I mean
with a normal transistor that means a large percentage of the base
current is not being amplified. Is it sort of the same with an
optocoupler? Or is this just the lowest that VCE for the part to
conduct current?
Similarly - with just a normal transistor optocoupler, what would a
VCE saturation voltage mean?
Also, are there any major advantages between transistor optocouplers
and darlington optocouplers? From what I can see, you have a much
higher (~5-10x higher) current transfer ratio with a darlington, but
you also have a higher VCE saturation voltage (about 1V as compared to
about 0.1-0.2V). Is one kind faster than the other, or are there any
other major differences?
Thanks!
-Michael
side switching circuit (as discussed here a month or so back). I was
recommended the FOD617 optocoupler, but I'd like to find a similar if
not better surface mount part.
I'm looking at using a darlington optocoupler. I think the Sharp
PC452J00000F looks nice, with a 1000% current transfer ratio at 1ma.
The datasheet for the part mentions a VCE saturation voltage (http://
document.sharpsma.com/files/pc452_eJ.pdf, figure 8) of about 1V. What
does a saturation voltage even mean with a phototransistor? I mean
with a normal transistor that means a large percentage of the base
current is not being amplified. Is it sort of the same with an
optocoupler? Or is this just the lowest that VCE for the part to
conduct current?
Similarly - with just a normal transistor optocoupler, what would a
VCE saturation voltage mean?
Also, are there any major advantages between transistor optocouplers
and darlington optocouplers? From what I can see, you have a much
higher (~5-10x higher) current transfer ratio with a darlington, but
you also have a higher VCE saturation voltage (about 1V as compared to
about 0.1-0.2V). Is one kind faster than the other, or are there any
other major differences?
Thanks!
-Michael