Positive/Negative voltage trigger controlled switch circuit

[_Vendetta_]

Hello EEVbloggers,

I would like to design an electronic switch circuit which turns ON when you apply a postive trigger pulse voltage and turns off when you apply a negative trigger pulse voltage. I exampled out the circuit behavior as depicted by the figure below:



I wonder if the circuit is achievable through transistors and some other passives..
I would like to have some ideas or maybe some references i can go through !

Thank you in advance.

[Zero999]

A Schmitt trigger will do that.

C1 and R3 ensure the circuit starts, with its output low. If you need it to start, with the output high, connect the other side of C1 to -V, instead of +V.

[_Vendetta_]

Thank you. I always had the idea of using the schmitt trigger for this. Would it be possible to use a single supply OP amp ( V+ connected to 3.8 Battery and V- to the ground) while still keeping the same behavior.

[Zero999]

Thank you. I always had the idea of using the schmitt trigger for this. Would it be possible to use a single supply OP amp ( V+ connected to 3.8 Battery and V- to the ground) while still keeping the same behavior.

Yes, but it's a little more tricky.

Note that the thresholds depend on the supply voltage, so you'll need a voltage reference, if you want them to remain fixed, irrespective, of the supply voltage.

[David Hess]

It is also known as a Schmitt multivibrator which might help finding examples.  Below is a two transistor version used by Tektronix in their PG505 high voltage pulse generator.  They are often used to transfer DC information across an AC isolation boundary like a transformer.

[_Vendetta_]

@Zero0999 Yes i see what you have done right there. You gave it a little DC shift bias usign that divider. much appreciated buddy !
@David Hess, Yes i know that type of schmitt trigger (called emitter coupled), if that circuit proves good stability and frugal energy consumption, i will go with it. Thanks again.

[David Hess]

@David Hess, Yes i know that type of schmitt trigger (called emitter coupled), if that circuit proves good stability and frugal energy consumption, i will go with it. Thanks again.

It does not have to be emitter coupled.  That was just the example I had immediately available.

A modern integrated comparator like you used is probably the best way to go unless you have a special requirement.

[Zero999]

An AC coupled solution might not work in this case, because it's triggered by the rate of change of the input, rather than the absolute input voltage. This means the output will go low on every negative edge, irrespective of whether it crosses zero, or not.