Formulas & Data:
- Electronics
- Mathematics
- Physics
- RF & Microwaves

Parts Vendors:
- all hand-selected

- Amateur Radio
- Vintage Articles:
- Electronics World
- Popular Electronics
- QST
- Radio & TV News
- Radio Craft
- Short Wave Craft
- Wireless World

- Events Calendar
RF Cafe Homepage
Copyright 1999-2015   •−•  ••−•    −•−•  •−  ••−•  •   "RF Cafe" in Morse Code  >> Listen to It <<
- EW & Radar Handbook
- Quizzes       - Software
- App Notes
- Calculators
- Advertise on RF Cafe
- About RF Cafe™
- RF Cafe Shirts & Mugs
- RF Cafe Archives
RF Cafe Book Contest
- RF Cafe on Visit RF Cafe on Facebook Visit RF Cafe on Twitter Visit RF Cafe on LinkedIn
- Tech Humor
- Forums Archive
- Job Board
- Donate to RF Cafe
- Kirt's Cogitations
Custom Search
More than 10,000 searchable pages indexed.
Greetings: There is so much good stuff on RF Cafe that there is no way to list or link to all of it here. Please use the Search box or the Site Map to find what you want - there is a good chance I have it. Thanks!

Setup question for signal source and buffer - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


Mr.Whatever
Post subject: Setup question for signal source and buffer Posted: Fri Oct 27, 2006 11:10 am

Captain


Joined: Fri Apr 07, 2006 6:10 pm
Posts: 18
I need your practical opinion from experience, if any. I have a signal source. Part of this signal needs to be sampled. One sampling process involves detecting whether the signal is there or not. Another sampling process will try to detect whether the signal amplitude has surpassed a certain threshold.

Just assume that the signal is a low frequency signal at 38 kHz.

Would it be optimal to do the following setup?

- use a quad opamp package and configure three of the opamps as voltage buffers / follower.
- tie the input of the three opamps to the same node
- connect the signal source to this common node

The first opamp would just replicate the signal source and send it unprocessed. The 2nd and 3rd opamp would do the sampling processing schemes.

Does this sound right?

Or would it be ok to skip the buffer setup and directly interface the signal source to a common bus that branches off directly to the sampling sections? This is assuming that the two sampling schemes utilize op amp inputs to do the signal detection and peak detection. Thanks!


Top

nubbage
Post subject: Posted: Fri Oct 27, 2006 11:22 am

General


Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
At such a low frequency, I would have the first OA as a voltage follower/buffer.
The output would go to the second stage as a full-wave detector with a time constant well in excess of the carrier cycle time (ie LPF).
The output would split two ways.
One way to a Schnitt Trigger to act as the "Signal/NOT signal" output, with the trigger level set just above noise (assuming this level is predictable).
The second way would be to another Schmitt Trigger with an adjustable trigger threshold set to whatever level you are looking for.

If only we had a simple Drawing Tool.



Posted  11/12/2012

Your RF Cafe
Progenitor & Webmaster

Click here to read about RF CafeKirt Blattenberger… single-handedly redefining what an engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5th MOB: My USAF radar shop

Airplanes and Rockets: My personal hobby website

Equine Kingdom: My daughter Sally's horse riding website