ADA4350 drive AD9650

I'm using the ADA4350 to drive the AD9650. The front-end circuit of AD9650 is shown below. The sample rate is 20MHz.

  

When I input a 100KHz sine wave to the ADA4350, The sample data is a stepped sine waves when ploted.

I have another PCB of AD9650. It's front-end circuit is ADA4938. When I input a 100KHz sine wave to the ADA4938, The sample data is a normal sine wave when ploted.

Is there anything special to care for when driving AD9650 with ADA4350? How can i drive AD9650 with ADA4350?