I am using the AD9954 to generate a continuous sine wave of 1 kHz, using an external 10 MHZ clock. I have chosen the DAC output network based on the excel spreadsheet found in the TI
"Interfacing op amps to high-speed DACs, Part 1: Current-sinking DACs" link here. I have set the output current to be 5mA, AVDD, 1.8V, 1V pp for Vdac (on IOUT pin) and Vout (after op amp) Below is a screenshot of the circuit.
Unfortunately I have measured a poor THD on the scope, around 3% or -30dB, which I am assuming is a result of the design of the filter circuit. I suspect the voltages are out of compliance for the IOUT pins, but I am not sure.
I have included a screenshot from the scope: Yellow is Vout (after the op amp) and the Red and Blue are IOUT and -IOUT. The clipping in the IOUT signals are clearly visible.
Any help you could offer would be greatly appreciated. I was expecting to be able to get something more like -60dB THD at least!