With a 2k load and 50pF you can get: Fmax=1/(tplh + tphl) For Fairchild DM74LS14 you get: best case - Fmax = 1/(8 + 10)nS = 55MHz worst case - Fmax = 1/(25 + 33)nS = 17.2MHz so you pick which one you like more. If I remember correctly, the tplh and tphl on the datasheets are specified for one device only. That means, if several of your inverters switch at the same time you might have troubles. TI used to have a very good AN, about all this. I think it was "designing with logic" or something like that, worth to check. VV Luis Moreira wrote: Hi guys can someone tell me the frequency that a 74LS14 can work up to. regards Luis -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu --------------------------------- Do you Yahoo!? Yahoo! Mail SpamGuard - Read only the mail you want. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu