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I made a circuit in which data is passed in from phototransistors (part# PT334-6C) into a microcontroller (part# AT89C4051) serial port via schmitt trigger inverters (part# 74HC14) and a demultiplexer (part# 74HC151).

I do have an option to replace the schmitt trigger inverters with standard inverters (part# 74HC04).

From what I learned, a schmitt trigger is meant to clean up and digitize a signal. Inputs that change in voltage by a tiny amounts when the voltage is slightly above half the supply won't be noticed in a schmitt trigger where as in a normal inverter they may be more noticed because a schmitt trigger requires the input to enter a lower or higher third of the VCC voltage to change output (I think that's the theory).

What I want to know is would a schmitt trigger work beautifully if I had data (of any value) flowing through it at the rate of 115,200 bps? Or are there any properties of schmitt triggers that prevent high speed data flow from working (in which case I'll have to resort to a standard inverter)?

And if there is a better schmitt trigger that is more suited to high speed data in the 74 family of chips, which one is recommended and why?

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    \$\begingroup\$ Mike, just try your HC14's. Even if you run them on 2 V, they are fast enough for your stated needs. And if you run them on any higher voltage, they will be several times faster still. Why not just try it and see? Do you have a scope? \$\endgroup\$ – jonk Jul 28 '18 at 2:16
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    \$\begingroup\$ Mike you are mistaken in thinking they convert a non-digital signal to a digital signal. What they do it take a slightly messy or distorted digital signal and try to restore sharp rising and falling edges with clean DC levels. They can do no more than that. \$\endgroup\$ – Sparky256 Jul 28 '18 at 2:40
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HC14's are your friend in this space. If you need faster response speed look at the faster logic families such as ACT14.

If you need more precise control over thresholds then build your own circuits using comparators. Comparators are available in many speed and power grades to meet a large range of design needs.

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You might even build this

schematic

simulate this circuit – Schematic created using CircuitLab

This should (barely) work. Improving the "barely" may be fun.

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