component circuit alternative to CEMs and such?

[LLP33]

Forgive me if this question sounds dumb or has been asked before, but i was
wondering if such specialized chips such as the CA3084 or the CEM chips could
be substituted with circuits made from more common components? i understand
some multi-transistor chips are required to be housed as one unit for
temperature stabilization purposes, or am i wrong? what are your thoughts? 
cheers,
C.F.