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Inverter/NOT gate question

Discussion in 'General Electronics Discussion' started by driverman, Jan 21, 2014.

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  1. driverman


    Jan 21, 2014
    So I was working on building a circuit involving an inverter earlier (Pierce oscillator), but after building it, it did not behave at all as expected (or at all coherently). I figured that my inverter was probably to blame, as it wasn't as complicated as the schematics that I had seen in the wild for an inverter (it was basically the simplest one I could find). Still, even though I knew it would most likely fail, I wanted to see how it would fail and why. So, I took a 74LS04 and hooked its input to the output of a 555 timer IC, and this is what I got (channel 1 is 555 output vs ground, bottom is 555 output routed through 74LS04):


    But with my crummy 1 transistor "inverter," this is what I got:


    Here is the circuit for the circuit that didn't work as I had hoped (there is a resistor on the input, I forgot to put it in):


    I'm not surprised that my circuit doesn't work, but I want to know why my one transistor NOT gate does not work. It almost seems like it takes too long for the transistor to "shut" when the input signal from the 555 goes low? If that suspicion is correct, then why does the hex inverter have such a fast response time?
    Last edited: Jan 21, 2014
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Show us the full circuit (including the oscilator) with component values and nte the points that you're connecting the probes to.
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