problem of pipelined adc

[lhlbluesky]

for a pipelined adc,how to obtain the transfer characteristic curve of vout~vin?
i.e. in the first stage,i want to know whether it works well,so i need to obtain the transfer characteristic curve of vout~vin,but when i simulate it in ADE using dc analysis (dc---design variable),the curve is not correct,it's only a straight line which has output voltage amplitude of 100uv or so ,and the CM output of vout+ and vout-
is only 210mv or so,confused,why?
how to obtain the transfer characteristic curve of vout~vin correctly?
pls help me.

 

[safwatonline]

usually using transient simulation with a ramp input