Electronics > Beginners
Dual Comparator Output Is Phase-Shifted
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epicode:
Hello, I've been working on a boost converter for a long time now and my control system needs to provide two high frequency inverted signals (when one is high the other one has to be low) and I've been using two comparators for that, both of them get a voltage reference (some constant DC voltage) and a triangle wave just that the inputs are swiped so that the required signal can be generated but for some reason the two signals are phase-shifted like the attachment below, I've checked the triangle wave and it is in perfect sync in both inputs.. the op amp is OPA2691I and as you can see in the picture the op amp seems to trigger in a weird way.. any ideas ?
dmills:
Um, you are aware that that is a CURRENT FEEDBACK opamp?

You cannot use that part as a voltage comparator in the way you seem to be attempting, because the inverting input is a low impedance (few tens of ohms per the datasheet) not high Z like a voltage mode opamp would be.

There is a trap in using opamps as comparators anyway in that many of them have an internal back to back diode pair across the inputs, if you want a comparator, use a comparator, there is a reason they exist.

epicode:
Thank you for the reply, I will try changing to LT1720 and see if that makes any differance
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