Sine wave antisipator circuit

Harry D · 2011-05-20T18:59:41+00:00

Ok, I have a 1.0Vac, 100KHz sine wave in a control loop that I wouldlike to use as input to a zero crossing detector but it has a 90d lagdue to BW limitations so how do I reconstruct this waveform to obtaina similar signal with no delay to yield accurate (+/-5%) ZC? A 90danticipator circuit would work but only for rookies. So I need 270d ofadded delay and some gain would be nice for noise immunity. Aninverter gives 180d and two poles at 45d each would add up to theneeded 270d. How can this be done with one op-amp? Is there a simplerway? The input signal may vary by +/-20% in frequency and I would liketo track the ZC somewhat. As the frequency decreases I will need morephase delay to make up for the reduced input delay but the newcircuit, if a filter, will yield reduced delay. That sounds like aPLL but is there a simpler way? Cheers, Harry

May 20, 2011 29 Replies

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John Larkin 15 years ago

If you were concerned about the last tenth-degree of phase shift at

100 KHz, you might fire up LT Spice and plug in various opamps.

John

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Phil Hobbs 15 years ago

Sure, and it would lie to you, but you'd feel much better.

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs (atsign) electrooptical (period) net http://electrooptical.net

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Harry D 15 years ago

lag

ike

one: (928)428-4073

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Don, you are killing me, PLL and counter. I just checked your "Active Filter Cookbook" and it only has one mention of an "All Pass filter" with no schematic nor equations. As is mentuioned in this thread, no simulation is necessary except to see how constant the gain is over the 0 to 180d phase shift. Ok, back in 75 that book was very helpful, used it for maybe 10 years then moved on. Thanks, Harry

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