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Analog signal to Digtal system

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roddyalan

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Hey guys,

What would happen to an analog signal being supplied to a digital system.

Like say for eg. I supply a +3V to -3V analog signal to a FPGA which can take inputs of 3V.

This Q has been bugging me for days and will help me sort out some of my digital problems.

Thanks
 

The negative 3 V will be a problem; clamp the input with a suitable diode.
The FPGA will "read" the input voltage of more than 2.3 V as a binary 1 and less than 2.2 V as a zero
 

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    roddyalan

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Thanks for the response. I was asking hypothetically.

So, are you saying that if I'm looking to make the positive analog signal into a one bit digital signal, with a really bad transition "area", i don't need an adc.

What happens if the analog signal is at 4V, but the input max voltage is 3V

Also, will the negative part just get clipped, and/or will it cause any other problems.

Regards
AR
 

roddyalan said:
So, are you saying that if I'm looking to make the positive analog signal into a one bit digital signal, with a really bad transition "area", i don't need an adc.
If you bear in mind that anything can happen in the transistion area (1, 0, both, not really either) then you might think that is not really acceptable.

What happens if the analog signal is at 4V, but the input max voltage is 3V
Click to expand...

You destroy the device. Another posssibility is that the source of the analog signal can't really cope with being able to supply the required current, but this is more likely to cause malfunction of the source circuit (or no effect) than damage to the source.

Also, will the negative part just get clipped, and/or will it cause any other problems.
Click to expand...

Yes.
If the source can suppply enough current, it will damage the fpga. Maybe it can't, and in this case the signal will be clipped. Maybe the source will be damaged, although this is less likely with typical sources.
Click to expand...
Click to expand...
 

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    roddyalan

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