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schematic

simulate this circuit – Schematic created using CircuitLab

I'm measuring a propagation delay and transition delay of a 74HC86 chip. I setted somewhat high frequency square-wave signal(100kHz) for Input 1. Input 2 was connected to VCC. I tried to measure delays, but oscilloscope confused me because of attenuation.

As you see in the picture, when the falling edge occurs(Yellow plot is the input of the 74HC86, and green plot is the output of the 74HC86), something like damping is shown and I'm frustrated because I don't know how to set the interval of measurement.

I searched some questions and I acknowledged that main cause is the L or C components in my probe, the breadboard, or my wire. However, I think this cannot be entirely disappeared, and I want to get the transition delay.

Is it okay to get the 0.1Vcc and 0.9Vcc as interval for transition delay? If it isn't, have to I modify the measurement points?

The link of datasheet of the chip is at below:

https://assets.nexperia.com/documents/data-sheet/74HC_HCT86.pdf

You can refer about the delays at page 7.

enter image description here enter image description here

  • I don't have a USB flash, please understand about this.
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    \$\begingroup\$ in the absence of hysteresis, CMOS gates are designed for VDD/2 switching behavior IMHO. So I'd measure from VDD/2. \$\endgroup\$ May 3, 2019 at 4:08
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    \$\begingroup\$ DSO1012A documentation. You need the manual for the 1000 series oscilloscopes. If it asks for a user name and email address, give it [email protected] \$\endgroup\$
    – JRE
    May 3, 2019 at 5:45
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    \$\begingroup\$ Screenshots on page 112 (chapter 5, section "To save screens to BMP or PNG format files") of the english manual. You will need a USB flash drive. \$\endgroup\$
    – JRE
    May 3, 2019 at 5:47
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    \$\begingroup\$ Unless otherwise specified in the datasheet, propagation delays are normally measured at the 50% point, transition (rise/fall) times are measured at the 10% and 90% points. \$\endgroup\$
    – Mattman944
    May 3, 2019 at 7:16

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