I generated two different Signals using DDS and now I want to add them and convert output signal to current signal without any distortion in it? what is the best and accurate part I can use ?
You can use opamp summer circuit for adding two signals.See the link below for detailed explanation. https://www.electronics-tutorials.ws/opamp/opamp_4.html
Then again use opamp at the ouput stage to convert V(voltage) to I(current).(V to I converter) .see the link below https://wiki.analog.com/university/courses/electronics/text/chapter-4
Ask if you have any doubt regarding this explanation