Setting trigger threshold on CMOS logic gates?

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Let's say I want to convert a 4V pulse to a 12V one.

How do I set a CMOS gate to register an "on" state at +4V, even though the supply voltage is +12V?

[Grumble]

I think the easiest way is to use a level shifter, these are ic's designed to do just that.
http://www.ti.com/lit/ds/schs369/schs369.pdf

[PHOBoS]

hmm from 4 to 12 is a bit much otherwise you might have been be able to get away with adding an offset voltage to the input with 2 resistors.
I haven't tried that though. Usually I add a transistor to the input (which also inverts but that can sometimes be useful) or you could use a comparator.

I am not familiar with the CD4504, looks interesting.

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[PHOBoS]

hmm I'd need a bit more information. If it is running on 6V it would be pretty tricky to get 13v out. You'd need a voltage doubler and some
other things or at least get that voltage from somewhere. However, adding a circuit to inputs so they work on a lower voltage shouldn't
be too hard. Forget what I said about adding an offset voltage, you can't just simply add voltages together

I think a comparator made with a single opamp would probably be the easiest solution and you could use a trimpot to set the reference voltage
which would make it easy to calibrate.

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[PHOBoS]

ah ok, if you already have the 13V available it is pretty easy to do with a comparator. Add your 6V clock signal to
the non-inverting input of an opamp, which you power with the 13V, and use a voltage divider (either 2 resistors or a
trimpot) to add a reference voltage of say 3V to the inverting input. If the clock signal is below this reference voltage
the output of the opamp will be 0V* and if it is above it the output will be 13V*.

*in reality it will a bit above 0V and below 13V depending on the used opamp

[Grumble]

If you prefer to use an opamp, why not use it as a Schmitt trigger?
Just one more resistor as in a comparator and, especialy when your edges of your signal aren't fast, are less succeptible to noise.

http://neurophysics.ucsd.edu/courses/physics_120/AoE_Comparators.pdf

[PHOBoS]

As far as I am aware turning it into a schmitt trigger by adding hysteresis only works if you swap the inputs and then it inverts.
Since the signal is already digital (and I assume we are not talking about very high speeds here) I don't think it is needed anyway.

[Grumble]

Non-inverting schmitttrigger, bron: https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-071j-introduction-to-electronics-signals-and-measurement-spring-2006/lecture-notes/24_op_amps3.pdf

Drawback is this has a hysteresis around gnd level, so would you want to use it, there will be a need for a voltage source.

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[PHOBoS]

oh nice, I'm not sure if I have seen that before. It does make sense though to just add the feedback to the input signal.