At 01:51 AM 1/18/02 +1100, Roman Black wrote: >Use a 2 resistor divider to set the schmitt input >to the mid-point between the HI and LO thresholds, >then capacitor couple the ac signal which should >then work the schmitt. 2 resistors 1 cap. :o) There is an old trick that allows automatic setting of the bias point: use 1 section of schmitt trigger inverter as a high speed oscillator, then use large value resistors to couple the input of that (osc) inverter to the inputs of the remaining inverters in the package. The signal at the input of the oscillator section ranges from VinH to VinL and the input capacitance of the inverters actually being used filters out (integrates) the high frequency signal, leaving a DC voltage exactly midway between VinH and VinL. dwayne Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 18 years of Engineering Innovation (1984 - 2002) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics