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Frequency Response Analysis (FRA)


riscy00

Question

I wish to do bode plot to validate the loop-gain feedback on switching regulator (Push-Pull on UC3825).

I'm thinking to buy PicoTest Injector Transformer costing $600 (is there cheaper version?).

I have Analogue Discovery (not 2) with BNC board.

What step I need to performs FRA with PicoTest Injector?, I can see it has Network option in Waveform and its sweep but I cannot see real application use for this type of evaluation. I can seen you have been working on AP300 unit to compare with this setup, any issue or progress. The scan range is roughly 10Hz to 1MHz.    

I'm very reluctance to consider CleverScope option so I very keen to get confidence based on this setup. 

BTW: Do I really need Analogue Discovery 2 to replace the old unit for this test?.

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Hi riscy00,

Those of here on the Digilent end of things (I can't speak for the community on this forum at large) don't have any experience with a PicoTest Injector or the CleverScope, so we can't really speak for them. I'm also not sure what you are referring to when you say "I can see you have been working on AP300 unit to compare with this setup"; I'm not aware of Digilent working with that particular product.

We have a tutorial on our reference site showing how to use the Network Analyzer: https://reference.digilentinc.com/learn/instrumentation/tutorials/ad2-network-analyzer/start, but I'm not certain what your question is. Are wanting to know how you would set up the software to run the network analyzer or how you would attach the leads on the Analog Discovery or something different?

As for your last question, no, you would not need the new Analog Discovery 2 in this situation over the original Analog Discovery.

Thanks,
JColvin

 

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Sorry for long absents.......

I would like to measure loop gain of the switching PSU and power amp (class D). I have injection transformer which is commonly used as part of loop gain injection signal. Please see https://wiki.analog.com/university/courses/electronics/electronics-lab-loop-gain. The question is why loop gain topic is not covered and how to use it for loop gain with injection transformer? is there sufficient in software to performs this task successfully?

Maybe it missing loop-gain documentation in Network Analyzer.  I attached a picture which I hope makes sense.... it seems the discovery has all need but no documentation. 

Capture.JPG

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Hi @riscy00

It seems to me that the referred hardware are software concepts are very similar to Analog Discovery and WaveForms.
Because of this the project could be executed with AD and WF.
With WF Network Analyzer you can also specify custom functions, add trace as reference for comparison.

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