Author Topic: Differencial probe 10x 1MHz using as8066  (Read 1665 times)

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Offline Apollo1234Topic starter

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Differencial probe 10x 1MHz using as8066
« on: January 26, 2024, 04:29:32 pm »
Hy there.

Recently i got challenged to build a differencial probe with 10x attenuation, 1MHz BW using a low cost op amp. I alreay unerstood the attenuator but im still stuggling with the op amp feedback compensation, i read some articles but cant quite understand what im doing wrong, can someone pls help me and explain what is going on? the hase goes like crazy and cant understand where is the problem
 

Offline MarkT

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Re: Differencial probe 10x 1MHz using as8066
« Reply #1 on: January 27, 2024, 09:40:22 am »
I'd be worried by low CMRR with that circuit - it relies on very accurately matched R's and C's for the attenuators and the differential stage. I'd suggest using a differential 10:1 attenuator circuit at the very least.

I don't think any compensation should be needed for your circuit, but it will need proper decoupling, and the output can't drive capacitive loads direct above 20pF, so 100 ohms on the output is wise.

BTW layout is critical for wide-bandwidth amplifiers, you haven't shown this.
« Last Edit: January 27, 2024, 09:49:02 am by MarkT »
 

Offline RFDx

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Re: Differencial probe 10x 1MHz using as8066
« Reply #2 on: January 27, 2024, 10:31:05 am »
The screenshot of your schematic is way to small (and compressed) to be readable.
 

Offline Apollo1234Topic starter

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Re: Differencial probe 10x 1MHz using as8066
« Reply #3 on: January 27, 2024, 05:19:09 pm »
I appreciate your understanding. I've recognized the issues with the CMRR, and I plan to address them by incorporating 0.1% resistors and a trimpot into the circuit. I had difficulty understanding the correct operation of the circuit initially, but now that I've gained clarity, I'll take into account real-world imperfections and work on resolving them.

It may take some time, but I intend to design a carefully crafted PCB and conduct thorough testing. If the results are satisfactory, I'll return to share the design files, in case you or others are interested in replicating it.

Thank you for your valuable time and assistance!
 

Offline berke

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Re: Differencial probe 10x 1MHz using as8066
« Reply #4 on: January 27, 2024, 06:29:07 pm »
Phase in grads :)
 

Offline RFDx

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Re: Differencial probe 10x 1MHz using as8066
« Reply #5 on: January 27, 2024, 09:41:37 pm »
Phase in grads :)

"Grad". Capital "G" and no "s" at the end.  :P
 

Offline bdivi

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Re: Differencial probe 10x 1MHz using as8066
« Reply #6 on: February 13, 2024, 09:27:50 pm »
Already built one several years ago. Works well up until 10MHz. A switch selects between x10 and x100.
 
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