Actions
Forum Thread Details
  • Replies 8 replies
  • Subscribers 595 subscribers
  • Views 727 views
  • Users 0 members are here
Related

Expected output voltage of XNOR gate

Andrew J

Hi,

 

I have a TI SN74HC266 XNOR gate.  If I pull two inputs high (4.9v) then the output should be high - what I'm seeing is 2.6V.  Is this right?  I may not be asking this the right way: basically, I'm trying to compare two inputs are either both high or both low and in either case, I want a high output to feed into a SN74HC08 AND gate.  I've checked the voltages on the XNOR pins and they are indeed high, but the corresponding output for that gate is 2.6v - I don't think that's enough to pull my AND gate high (at least it's output given 2 inputs at 2.6V is 0V.)  I've also checked the XNOR where the two input pins are 0V and the output pin is also 2.6V.

 

I can't tell from the data sheets if this is right, although I struggle to understand these in detail at the moment. 

 

Thanks

 

Andrew

Parents Reply
  • in reply to DAB

    Thanks Dab, that's all it needed.  I'm using a number of HC chips in the overall circuit and not needed pull up resistors to drive inputs down the chain (until I reached the 266) but I'm now measuring 4.9v on the output pins.  Something to file in my brain for the future. 

     

    Thanks again, I really appreciate it.

     

    Andrew

Children
No Data