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Off voltage of LM311 with pin 1 grounded
(1/1)
aneevuser:
I have an LM311 where I've grounded pin 1, the pin that goes to the emitter of the o/p transistor. (Grounded here means connected to 0V with a +10V, 0V, -10V power setup.)
Am I right in thinking that the lowest voltage that I'm going to see on the o/p is \$V_{CE(sat)}\$ of said transistor, say, about 0.3V - or am I confused?
fcb:
Yes, in your present configuartion, you'll see VCEsat on the collector/pin7 (assuming you've got some sort of pull-up thing going on). You can take pin1 to -ve BTW
aneevuser:
Thanks.
I'm guessing that there's a fair bit of flexibility in setting the high/low o/p voltages, given that both the emitter and collector are brought to the outside of the device - these voltages seem pretty independent (within reason) of the power rail voltages to the device itself?
fcb:
Don't take it below the substrate voltage (-v).
David Hess:
Neither ground nor the output should be pulled below the negative supply for the reason fcb identified.
Ground may be up to 30 volts above the negative supply (according to the datasheet) and the output may be up to 40 volts (or more with some parts) above the negative supply. This would allow open collector operation with an output voltage higher than the supply voltage.
I am not sure why someone would raise ground above the positive supply but it is allowed. The output will not work then though.
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