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I am using an AD8933 and an Arduino as a simple signal generator. The Arduino is connected to the AD8933 via the SPI pins via connections on a bread board. The problem I am experiencing is there is significant noise observed on the output.

Sine Wave 5 Hz

Square Wave 5 Hz

While the rise time of the square wave looks good, it contains the same oscillation as the sine wave.

Any recommendations on how to diagnose this issue?

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1 Answer 1

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Looks like this supplier hasn't bothered to put much of an output filter on the board (maybe just a single capacitor), so you're going to get pretty horrible waveforms.

Better boards will have a multipole active or passive LC filter as this one (just as an example, no endorsement implied):

enter image description here

You may also be getting some switching power supply noise on the output. Try turning off the DDS output and increasing the 'scope sweep frequency to look for 50kHz to a couple MHz noise.

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  • \$\begingroup\$ My input voltage looks stable. Simply adding a 9k ohm resistor in series with the output stablized the output enough to get better quality signals. I will look into adding an LC filter when I have more time to diagnose the problem. \$\endgroup\$
    – Blackninja543
    Commented Jan 29, 2023 at 21:40

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