I want to know basic difference between series & shunt voltage referance . I am also interested in details of their implementation in different circuits.

It is good to see more articles on voltage references. I am not sure, however, if the comment under fig. 1, "the shunt reference is more precise and has better temperature stability" is correct. The comment appears to mean that shunt references have better specs than series references where series references are defined as three terminal references.

Yet, the best performing devices on the market today are generally three terminal references. For example, in the AD ad next to the FAQ, the ADR44x rated at 3 ppm / c with .04% initial accuracy appears to be a series reference. Other series parts, such as those offered by AD, TI, and Maxim approach tempcos of 1 ppm/c. It seems that the vast majority of references, both shunt and series run overlapping ranges of accuracy and temperature coefficient. The only exception I can think of is the remarkably accurate, yet costly and relatively difficult to use Linear Technology LTZ1000 shunt reference.

Another issue is that a less experienced engineer might inadvertently degrade the accuracy and temperature coefficient of a shunt regulator, since there is no built in low impedance output, as is the case of most if not all three terminal references.   Joe Geller GELLER (Geller Labs) http://www.gellerlabs.com