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The 74LVC1GU04 is an unbuffered inverter, which (according to the datasheet) is intended to be used in linear mode in applications, such as crystal oscillators and linear amplifiers with negative feedback.

But the same datasheet claims that there is a "Schmitt-trigger action" on the input. That is the standard formula meaning there is a small (100 mV) hysteresis on the inputs. All CMOS families use such inputs nowadays.

But even a small hysteresis on the input will definitely make it impossible to use the element in linear mode with negative feedback - it will simply oscillate.

Does the 74LVC1GU04 really have a "Schmitt-trigger action" input? Or is there a mistake in the datasheet and does especially this element have input without hysteresis?

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  • \$\begingroup\$ It looks to me like there is no hysteresis on the input. They don't specify it in the datasheet either explicitly or as different rising and falling thresholds. The logic diagram doesn't show anything that would provide hysteresis either. But maybe someone more familiar with the part can say for sure. \$\endgroup\$
    – John D
    Dec 20, 2022 at 23:01
  • \$\begingroup\$ @JohnD: Well, they never specify the parameters of the "schmitt trigger action" inputs. Only that they exists. Only the "real" schmitt triggers are explicitly specified with the threshold voltages and the hysteresis. \$\endgroup\$
    – johnfound
    Dec 20, 2022 at 23:33
  • \$\begingroup\$ Never? See P.7 of the following 74LVC family device: assets.nexperia.com/documents/data-sheet/74LVC132A.pdf \$\endgroup\$
    – John D
    Dec 20, 2022 at 23:41
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    \$\begingroup\$ @JohnD: 74LVC132 is "real" schmitt trigger, not "schmitt-trigger action". The real schmitt triggers are specified, of course, as I already said. \$\endgroup\$
    – johnfound
    Dec 20, 2022 at 23:47
  • \$\begingroup\$ Ah, OK, as an analog guy I didn't get the nuance between "Schmitt-trigger action" and "real" Schmitt-trigger devices. I stand corrected. \$\endgroup\$
    – John D
    Dec 20, 2022 at 23:53

1 Answer 1

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This is a copy-paste error. All other (buffered) parts in the 74LVC series have schmitt-trigger inputs, but the 74LVC1GU04 in particular does not. They simply forgot to delete that line from the document template.

Figure 3 in the datasheet shows quite clearly that there is no hysteresis. The part is just a simple two-transistor CMOS inverter with some ESD protection. Another clear indicator of that is Figure 9: the part has a well-defined transconductance (and therefore operates as a linear amplifier), which wouldn't be the case with schmitt-trigger inputs.

I've sent Nexperia an e-mail about it, they'll probably correct it soon.

Keep in mind that the part might dissipate excessive amounts of power when used as a linear amplifier at higher supply voltages due to cross-conduction. Operating it in linear mode with 5V supplies might be pushing things a little too far. You'll have to check for yourself if the chip overheats at your desired supply voltage.

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    \$\begingroup\$ The dual inverter74LVC2GU04 has a better data sheet without the Shmitt trigger inputs \$\endgroup\$
    – RussellH
    Dec 21, 2022 at 2:51

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