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I have a complex circuit, and I am dealing with a problem that appears. I have a RC circuit followed by a 7414 Trigger inverter. My input voltage is 90mV and after the simulation the output looks like this.(see first picture). And the circuit (see last picture.). So the question is why my Output at C27 isn't almost at the input voltage value like it should? enter image description here enter image description here enter image description here

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  • \$\begingroup\$ The TTL chip won't toggle with a 90 mV input signal anyway. \$\endgroup\$
    – Andy aka
    Mar 8, 2021 at 14:52
  • \$\begingroup\$ That signal 90 mV is from a D-Flip-Flop, when CLK is '0'. So this is how it's done in the article that I try to follow ( last picture from question) \$\endgroup\$
    – Julien
    Mar 8, 2021 at 14:58
  • \$\begingroup\$ Does anybody use antique TTL ICs anymore? \$\endgroup\$
    – Audioguru
    Mar 8, 2021 at 17:26

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Standard TTL inputs do not have a high input impedance, you need to use a much smaller resistor with this IC. Or, use a 74AC14, it has a very high input impedance; you will get the result you want with CMOS inputs.

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  • \$\begingroup\$ Thank you, very much! It works now! \$\endgroup\$
    – Julien
    Mar 8, 2021 at 13:15

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