Amplifier noise

Hi chandima,

Let me contact the Apps Engineer for this part and get back to you on your query. For now, can you provide more details on your scope shot? (schematic, probed nodes, target output, etc.)

Thanks,

Kristine

I built up this circuit shown on the picture. I am getting the scope output from highlighted in yellow. It should be clean square wave output but I am getting noise on it. Any idea about this

Hi Chandima,

Few things to check/clarify:

• At the highlighted part of your circuit, did you probe before or after the resistor? 
• Can you also probe your inputs and check if your signal is already noisy? if the input signal itself is already noisy, you may opt to change your signal source or probes/connectors. You can also add filter stages to your design to improve the quality of your input signal.
• If the noise is only seen at the output stage of the amplifier, what you can do is debug the circuit by isolating/probing per stage/node. This will allow us to understand what may have been the additional noise source in your circuit.

Hope this helps!

Kristine

kristinehoffman said:

At the highlighted part of your circuit, did you probe before or after the resistor? 

 I probed after the resistor.

I probed the inputs there wasnt much noise. Even if there is noise on the inputs how can it probate at the outputs of the amplifier. Because these are operational amplifiers.

Thank you

Hi chandima,

Apologies if I missed this thread.

The noise graph you attached seems unclear for me to analyze. Can you attach a clearer scope shot with X/Y axis present? There are several factors that contribute to noise, and with the reference design you are using, any of the amplifiers in the first stage could be contributing to it. Even measuring equipment or probes could affect noise and sometimes maybe the culprit for the spikes we see.

There are several provisions and input options in the diagram you attached, can you attach the link from where you found this design? If possible, can you attach a actual block diagram on what input levels are you using or being conditioned in your system, and also supply levels of the amplifiers specifically those before AD8253? In this way we can understand better on what may cause the noise jitters that you mentioned.

Have you also tried simulating it first on LTSpice? In this way we will be able to modify and configure the design and see the expected output first before fabricating it on bench.

Regards,

Kristine

Hi chandima 

I'm closing this thread for now, please reach out if you have additional questions for AD8253.

Thanks

Hi chandima 

I'm closing this thread for now, please reach out if you have additional questions for AD8253.

Thanks