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Setup question for signal source and buffer - RF Cafe Forums

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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!


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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.

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