OPA349: A time delay circuit ,what's the difference bettwen RC and operational amplifier design

user5264061

Prodigy 160 points

Part Number: OPA349

I want to design a time delay circuit, as the below design,what's the difference bettwen A and B scheme ？

over 4 years ago

0 Michael Steffes over 4 years ago

Guru 47485 points

FIrst of all, a better time delay would be a 2nd order Bessel active filter - linear phase is time delay.

The main difference in what you show is the op amp approach would have a low output impedance drive for whatever comes next. And, as you show it, you have two poles in that circuit.

0 kai klaas69 over 4 years ago

Guru 140200 points

As a delay correction in active loudspeakers, see the "allpass filters" in this link:

Kai

0 Former Member over 4 years ago

Hello,

As Michael has already mentioned, you'll have a more complex phase response. Additionally, some noise will be introduced to the system. Depending on your application, this level of noise may be acceptably small.

The big improvement is that you have you can use the amplifier output to drive whatever comes next in the signal chain, again as Michael has already mentioned.

Regards,

Daniel

0 user5264061 over 4 years ago in reply to Michael Steffes

Prodigy 160 points

Thank you for your reply. It's of great help to me.

0 Michael Steffes over 4 years ago in reply to user5264061

Guru 47485 points

I thought I had posted a Filterpro example all pass? Oh well, moving on to the webench example, clearly based on FilterPro with an interesting faux pas. I guess if you are in the business of selling op amps, you might think of those pesky passive vendors as parasites.

0 Pete%20Semig over 4 years ago in reply to Michael Steffes

TI__Mastermind 25775 points

Hello Michael,

Please understand that TI values our relationships with all suppliers/vendors. In no way, shape, or form does TI think of passive device suppliers/vendors as 'parasites', regardless of our business model.

What is a more logical explanation is that our web development team mixed up the terms 'parasitic' and 'passive'. So, thank you for pointing out this issue....I will send it on to our design tools team for correction.

0 kai klaas69 over 4 years ago in reply to Pete%20Semig

Guru 140200 points

Haha...

Yes, looks more like a simple typo.

Kai

0 Former Member over 4 years ago in reply to Michael Steffes

Michael,

As you can see below, the issue has now been resolved. Thanks for pointing it out.

Regards,

Daniel

0 Michael Steffes over 4 years ago in reply to Former Member

Guru 47485 points

Ah yes, an easy and useful fix,

Who should I invoice on this one?

0 Former Member over 4 years ago in reply to Michael Steffes

Michael,

Why send an invoice? The glory of 10 extra e2e points far outweighs any other form of compensation :)

Regards,

Daniel

0 Michael Steffes over 4 years ago in reply to Former Member

Guru 47485 points

Possibly, I will see if I can exchange those for malt beverage at my local watering hole.

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OPA349: A time delay circuit ,what's the difference bettwen RC and operational amplifier design