barry
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Two single ST gates and an AND.
What'S an ST gate?
I'm talking about circuit functions not IC packages. They asked about "designing" the Schmitt trigger although no technology has been mentioned yet.Just use a single ST AND, e.g., 74HC7001, or two NANDs. No reason to use two packages.
so how would i design this schmitt trigger with 2 inputs?
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another problem with this design is that the pulse will be stretched in a constant time regardless how long the input takes, which is applicable in case if the input is longer the RC time constant, so is there a solution to add this time constant to the original width?
Is this what you want, or not? If it is, my original suggestion does exactly this. I think it’s time now for you to provide more specifics of exactly what you want. Min/max input pulse width, output pulse width etc. it’s becoming less clear whether you want a pulse stretcher, edge-triggered one-shot, or what.View attachment 153709
here's and image of the output
The RC delay solution has the problem that the extension time reduced for short pulses because the capacitor isn't fully charged. This can be handled by a diode across the resistor.
Is this what you want, or not? If it is, my original suggestion does exactly this. I think it’s time now for you to provide more specifics of exactly what you want. Min/max input pulse width, output pulse width etc. it’s becoming less clear whether you want a pulse stretcher, edge-triggered one-shot, or what.
Bad idea. Use this:
View attachment 153653
Have to consider pulse width, etc. in selecting RC. Can also put diode across R for narrow input pulse.
What’s the duty cycle? If you have 500 ns pulses with a 50% duty cycle, there won’t be time for the cap to charge (as has been pointed out). And what’s the stretch-time? In order to do a proper design, you need ALL the information.
So you're going to need to put a diode across the R so that the cap charges fast.
You need to do some actual engineering here. Here's what you need to think about:
If you use the circuit I showed in post #12 you need to ensure that the input pulse is wide enough (low) to completely discharge the cap. You also need to ensure that the pulse high-time is long enough for the cap to completely charge. These are the limitations of this circuit. You can play some games with diodes; for instance, if your low time is short but your high time is long enough, you can put a diode across R to discharge the cap faster. If your requirements don't meet these limitations, you'll need to think of a different (i.e., more complex) approach.
I'm not sure what you're asking.
I still dont know what you mean by "realizing". What is your simulator?
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