Hi,
The following informations would help in understanding the promleb in more details....
1.What type r u using...MOS/BJT/BiCMOS....
2.Ref. voltages would be connected to MOS gate or BJT/HBT base....
3.What is the resolution of the reference voltahe...
In general, that much I know is, people go for resistor ladder network to generate reference voltage for FLASH ADC....now, if u can achieve a good matching between the resistors.....and throw a fixed current through them..it would do the work.....but, in ADC as the spec. is highly bound by two independent module.....one is Input Swing and the other is Resolution.....so u have to precisely control the reference voltage magnitude...in absolute value...not in ratio...thus if u throw current....the abolute value of the layed out resistor mulipled by the BGR current...need to be 'absolutely' matched with the ADC input swing and resolution....
Instead if u use a voltage bgr, then the upper level of the reference is fixed and stable....now if u just devide it to the required level with the resistors...it would be better..
In the second case....the configuration would be sensitive only to relative mismatch of the resistors...not the absolute value.....
This is a general talk...if u need more details plz be free to discuss...
sankudey