24 Volt AND gates?

18 volts (4000 series CMOS) is the highest voltage logic I am aware of. You may have to make your gates with diodes and comparators.

Thanks. I may just make them out of transistors. I found this:

Or relays, if easy availability is more important than size or power consumption ...

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Regards,
        Doug Miller (alphageek at milmac dot com)

It\'s time to throw all their damned tea in the harbor again.

this:

Becareful with that first example. If you applt +24 to the bottom transistor and ground to the upper one, you reverse bias the base emitter junction of the top one beyond it zener voltage, which will not only make the gate malfunction (the output high will be weak) the reverse base current will slowly reduce the gain of the upper transistor.

this:

I think diode transistor locic would work better.

this:

better.http://en.wikipedia.org/wiki/Diode-transistor_logic

Does that circuit require that the inputs be allowed to source current? I would be driving it with "high side" drivers that can't source current.

this:

Looking at the datasheet:

which value would I be concerned about to find out what the limit is on the zener voltage? Would it be the Base-Collector breakdown voltage?

Thanks. Jeff

this:

datasheet:

No. The base to emitter reverse voltage.

this:

better.http://en.wikipedia.org/wiki/Diode-transistor_logic

The diode transistor logicshown sources current out through the inputs that must be sunk to ground to pull the input low. And the schematic shown is a NAND, not an AND.

But the circuit can be rearranged for pull up inputs and converted to and. What must the output drive?

not just trannies... use a sprinkling of diodes too and it all becomes very easy and a very real proposition... if you start looking at circuits in this light, you'll be surprised how many include the logic primitives in this form. Sometimes I will use a DTL configuration rather than chuck a chip in and leave 3/4 of it unused (although I do weigh the costs in such a decision)

this:

better.http://en.wikipedia.org/wiki/Diode-transistor_logic

A motor controller that is expecting 24 volts signal to activate the drive. There's no serious current draw.

What does the input voltage go to when nothing is connected? In other words, must the gate output pull positive or negative?

an

this:

better.http://en.wikipedia.org/wiki/Diode-transistor_logic

While doing it in discretes is certainly possible, unless your logic is very minimal (less than 4 or 5 gates worth) it may be worth just throwing a regulator into the circuit and using standard gates.

I think that for anyone here to give an answer that really is the best solution (however you may chose to define best: (least cost, smallest, simplest etc...)) you need to give MUCH more detail about what you are trying to do.

Tell us the end result you are looking for, what you have already aquired hardware wise or are committed to not changing, where your inputs come from, etc.

I strongly suspect you should not be doing your logic at 24 volts, but should be changing another part of your circuit to take logic level (5 or 12 volt) inputs.

Martin

this:

Here's another:

this:

try this link for discrete logic gates