I know that I can apply the voltage to input and I can get output voltage same as the input, using ADG779. But I want to apply the constant current to input and get the output current same as the input. Is it possible? In other words, can I use the input and output of the ADG779 as current? If not, are there any products that are suitable for my use?
I am not entirely clear about what you are asking.
When the ADG779 channel is on, the channel consists of a NMOS and PMOS transistors in parallel. There is a resistance associated with the transistors so there will be a voltage drop as well as added leakage current. I hope this answers your questions.
Please see the following link to MT088 that describes the functionality of a standard CMOS switch. http://www.analog.com/media/en/training-seminars/tutorials/MT-088.pdf