i want to build a comparator to compare voltages such that reference voltage is negative

[A.N]

i want to build a comparator to compare voltages where
reference voltage is negative,a square wave is to be generated at positive cycles of zero crossings of sine wave

[Enrique]

I am having trouble in understanding your question (aside of my suspicion that this may be a school assignment 🙂 ). Please check my previous explanation about comparators in your previous question:

http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=5065000000080000008C2B0000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0

Also, check the following answer I provide for a current question about zero-crossing detection:

http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=5065000000080000008B2B0000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0

Also, check the attached vi (LabVIEW 5). The vi generate a sine wave, detect if the is greater or lower than zero and create a square wave accordingly.

Best regards;
Vargas

[Niko]

and your question?