Click on the pictures:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/3435
http://www.dabrahams.net/site/?page=projects-articles-rfdata
http://electronics.stackexchange.co...-circuit-to-generate-a-digital-pulse-from-ldr
http://electronics.stackexchange.co...ing-the-output-of-an-opamp-into-a-square-wave
What frequency do you want to decode?

Thanks.

 

It's a form of a Differentiator. The comparator with the normailzation capacitor is a way of getting rectangular pulses at the inflection points instead of the trailing trace of the capacitor-charging differentiator.

 

It's a form of a Differentiator. The comparator with the normailzation capacitor is a way of getting rectangular pulses at the inflection points instead of the trailing trace of the capacitor-charging differentiator.

You've got the resistor and capacitor back to front.

Its the exact opposite to a differentiator - which makes it the integrator someone said it can't be.

 

You've got the resistor and capacitor back to front.

Its the exact opposite to a differentiator - which makes it the integrator someone said it can't be.

No, the comparator circuit in this thread is definitely a differentiator. It's definitely not an integrator. It's just using the capacitor in a different configuration to normalize the output to the current level of the input. When the input deviates from that level, either positively or negatively, the comparator generates an output in the direction of the deviation and then returns to baseline. That's a differentiation.

It's just a digital differentiation, a "quantum" differentiation, if you will, versus the analog differentiation of the series capacitor.

 

Google "opamp data slicer"

 

You've got the resistor and capacitor back to front.

Its the exact opposite to a differentiator - which makes it the integrator someone said it can't be.

You are probably going to have to tell us what you want to do instead of us trying to guess.

 

Google "opamp data slicer"

Already tried that....................................

 

You are probably going to have to tell us what you want to do instead of us trying to guess.

I want to connect up a flashlight bulb - is it really necessary to write an essay on what I want it for?!!!!!

 

I want to connect up a flashlight bulb - is it really necessary to write an essay on what I want it for?!!!!!

Depends on what you want:

If you just want a name for the circuit, it sounds like data slicer is it. Plenty of references to it under that name, and no-one here seems to know it by any other name.

If you want help optimizing it for a specific application, then you'll need to share more about the application.

 

I want to connect up a flashlight bulb - is it really necessary to write an essay on what I want it for?!!!!!

No, it isn't. But those eight words are the first hint of what you want to do with the circuit. Up to now, the only question you have posed is about the name of the circuit.

ak

 

No, the comparator circuit in this thread is definitely a differentiator. It's definitely not an integrator. It's just using the capacitor in a different configuration to normalize the output to the current level of the input. When the input deviates from that level, either positively or negatively, the comparator generates an output in the direction of the deviation and then returns to baseline. That's a differentiation.

It's just a digital differentiation, a "quantum" differentiation, if you will, versus the analog differentiation of the series capacitor.

After that explanation, I understand why you refer to this circuit as a differentiator, although it certainly is an extremely limited form of one. Along that line of thought, a better name would be a slope detector, but that term has a well-established meaning that is quite different. Also, it actually detects only reversals of slope, and intentionally ignores all other changes in slope. So I guess it actually is a double-differentiator...

ak

 

I want to connect up a flashlight bulb

How many forum posts does it take to connect a light bulb?

 

How many forum posts does it take to connect a light bulb?

Depends on who's asking.

ak

 

How many forum posts does it take to connect a light bulb?

There's a few on here could spin it out about a year....................

 

After that explanation, I understand why you refer to this circuit as a differentiator, although it certainly is an extremely limited form of one. Along that line of thought, a better name would be a slope detector, but that term has a well-established meaning that is quite different. Also, it actually detects only reversals of slope, and intentionally ignores all other changes in slope. So I guess it actually is a double-differentiator...

ak

I think it detects any inflections, even two in the same direction. So it's not just "reversals". Just any inflection. Which is, of course, a "differentiator." But definitely a peculiar one. A quantum-output differentiator, change-detector with directional elements...

 

I think it detects any inflections, even two in the same direction.

Nope. Think about it. If the + input is greater than the - input and moving upwards, the - input continually lags because of the R-C delay. As long as the + input continues to increase, whether more or less quickly, the - input never catches up.

Only when the + input reverses slope, *and decreases by a voltage amount greater than the voltage drop across the resistor at the time of the reversal*, will the output change state.

If the + input continues to increase, but so slowly that the - input gets to within the input offset voltage error, then the output can change state incorrectly. So the R-C time constant must be selected to operate with the maximum pulse width in either state.

ak

 

I definitely see what you're saying, AK. But it seems your assumption is that it's a monotonic signal. If the signal has flat discontinuities -- flattening of slope so the capacitor side of the op amp catches up with the direct-input side of the op amp -- it can still register multiple inflections in the same direction (increasing or decreasing) without an actual "change" in direction. It is a relative change, to be sure, but it seems to me all it would take is a leveling of the signal for enough time to overcome the R-C time constant. The output would zero, and it would be ready to be triggered by the next inflection, whether in the same slope direction or a reversal.