  We discuss the one-loop effective potential and static (large $d$) potential
for toroidal D-brane described by DBI-action in constant magnetic and in
constant electric fields. Explicit calculation is done for membrane case
($p=2$) for both types of external fields and in case of static potential for
an arbitrary $p$. In the case of one-loop potential it is found that the
presence of magnetic background may stabilize D-brane giving the possibility
for non-pointlike ground state configuration. On the same time, constant
electrical field acts against stabilization and the correspondent one-loop
potential is unbounded from below. The properties of static potential which
also has stable minimum are described in detail. The back-reaction of quantum
gauge fields to one-loop potential is also evaluated.
