Reduce Noise using a Capacitor

Hi I wanted to reduce noise using an SMD capacitor, the plan is to solder it between pins on a PCB. Any suggestions how to calculate the correct farads?


We are looking into this request and will get back with some ideas.

Thank you


Ignoring parasitic phenomena, a capacitor has an impedance of -J/(2πFC), where:
J is the imaginary unit
F is the frequency (in Hz) being evaluated
C is the capacitance value of the device.

This value is used to represent the device in circuit analysis calculations, such as of a voltage divider or RC filter.

The degree to which placing a capacitance between two nodes in a circuit reduces any signal present between them is a function of signal frequency, the impedance of the source driving that signal, and of course, the capacitance value. Some combination of running the numbers and a “try it and see” method can be used to reach a solution; the former approach reduces unnecessary effort, while the latter reveals errors in calculation or apprehension and is, at the end of the day, the means by which a solution is demonstrated.

Thank you for the information, I will give it a try.

Hello @wil,

Please allow one additional comment.

Measuring noise on a circuit board can be a challenge. Often folks use the long oscilloscope ground clip which results in inaccurate readings.

Recommend you use the spring-loaded ground tips as shown in this image.

Best wishes,


P.S. Recommend all readers review ABCs of Probes Primer | Tektronix.


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Thanks, I will double check what we have in the lab.

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