I am currently using AD9834 making use of its capability to have sine, triangle and square wave outputs.
My application needs a 10MHz cut-off frequency. When I tried to populate an RC filter (with Fc = 10.61MHz) in the AD9834 eval board, the sine wave output is not that good thus I decided to choose other type of filter.
I was able to see this thread http://ez.analog.com/thread/7281?start=0&tstart=0 and downloaded the attachment of LiamR in which a 1st order and 3rd order schematic with corner frequency of 3.3MHz is provided. I tried to simulate it using the Nuhertz Filter Solutions trial version in which I came up with the same, and I was also able to simulate for 5th order. Attached is my filter solutions screenshots.
I am working at this first before going to 10MHz cut-off frequency.
However, when I tried to simulate the generated schematic in MultiSim, the response seems to be different.
This is the Multisim simulation for the 1st order.
In this 3rd order simulation, instead of having a corner frequency of 3.3MHz, the -3dB frequency is just around 475kHz.
When I proceeded to 10MHz, still the same.
Instead of a 10MHz at -3dB bandwidth, it's just around 2MHz. Can someone advise on this?
Thank you very much.