Feeding a CMOS input from a TTL output is a bit more problematic as the TTL output of 2.4V in a 5 volt system is not high enough to guarantee a High is seen by the CMOS part.

CMOS and JFET-input op amps are often selected for their low input bias current (I B). But there is more to the story than the single line in a spec table—subtleties that you should be aware of. The ...

Figure 2 Schematic diagram of wire break detector using CMOS memory cell (shown in broken box). If using the CD40106, only one gate is needed for the oscillator (Schmitt inputs). An additional gate ...