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Attenuation of higher frequencies

saurabh17g

Mar 8, 2010
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Mar 8, 2010
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Hello,
I am utilizing AD9833 to generate waveform to 10Mhz according to datasheet.
But after 50KHz, I am getting attenuation. DC level gets added and distortions as well. At 100K, the response is almost DC. I am not able to figure out the reason of such behavior.
I was expecting that these things would occur after 1MHz. But 50K is too early :(

Please give me suggestions and possible solutions.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Perhaps a circuit diagram might be helpful?
 

saurabh17g

Mar 8, 2010
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i have attached the circuit diagram.
it is according to the datasheet of AD9833.
 

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  • circuit.jpg
    circuit.jpg
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
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I hope you're not using C4 in your circuit.
 

saurabh17g

Mar 8, 2010
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I put 100nF as C4.
There was a problem in PCB and IC was SMD. So, it was desoldered and resoldered. would that be the reason for high frequency attenuation?
 

Mitchekj

Jan 24, 2010
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Jan 24, 2010
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Try taking C4 out, it's shunting your high frequency to ground. The higher the frequency, the less impedance the cap has to it.
 
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