Building a Custom Schmitt Trigger with Variable Trigger Points

[soidal]

Hello,

I'm looking for inexpensive schmitt trigger that has variable trigger points (30v - 50v) and that will handle max current of about 3A. I would very much appreciate your pointers.

PS
Are there schmitt triggers that triggers at certain negative voltage? (for example, does not trigger at -39v but triggers at -40v)

 

[NoTime]

An op-amp can be wired as a schmitt trigger.

 

[berkeman]

Hello,

I'm looking for inexpensive schmitt trigger that has variable trigger points (30v - 50v) and that will handle max current of about 3A. I would very much appreciate your pointers.

PS
Are there schmitt triggers that triggers at certain negative voltage? (for example, does not trigger at -39v but triggers at -40v)

That is something that you should make out of discrete transistors that will handle the voltages and currents that you specify. Do you want a differential input or a single-ended input? You will basically build up the basic circuits of an opamp/comparator (as NoTime says), and close a positive feedback loop to give you the Schmidt trigger hysteresis characteristic that you want. If you are more specific in your requirements, we can suggest some circuit topologies for you to consider and experiment with.