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AD9833 Maximum Freq out & Filter design

Question asked by Kapil on Sep 14, 2011
Latest reply on Sep 14, 2011 by LiamR

Dear Sir,

         I am Jayaraj, from India. Using AD9833, for one of my project.I am able to write & vary the frequency of sine, triangle & square waves using my uC & LCD & keypad. Now I am in the process of fine tuning.

         My system design plan is 0-1Mhz with an amplitude of 2Vp-p, of all the 3 waves with a MCLK of 25Mhz.

          I am using 35MHz bandwidth OPA350(non-inverting) with a gain of 6.5, on the output of AD9833, without any filter. The SINE & TRIANGLE WAVEFORM output looks good enough, when I see on the output of the amplifier OPA350. And the square wave is bypassed from the amplifier and terminated.

         Doubts:

                 A. I am finding a small glitches on the edge of the square wave. Reply me, what combination of resistor & capacitor value (on the output of AD9833) will give a good filter output, for all the 3 waves? Or shall I insert a capacitor in my op amp feedback loop? if yes,What value?

                  B.  Also reply me, the range what I had selected 0-1MHz for sine wave & triangle wave will it be okay, wrt to 25MHz MCLK?

                 C.   Does the amplification makes any signal smoothening for higher Fouts? Because I was able to see a good sine and triangle wave, even at 1.5MHz freq out (trial, wrt MCLK of 25Mhz), only with a small amplitude reduction. But your support forum, answers are inidcating to work on less frequency.

                 I am unable to attach my schematic. I am expecting positive reply for the above doubts.

with regards,

Jayaraj.A

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