  We find a class of flat supersymmetric brane-antibrane configurations. They
follow from ordinary brane-antibrane systems by turning on a specific
worldvolume background electric field, which corresponds to dissolved
fundamental strings. We have clarified in detail how they arise and identified
their constituent charges as well as the corresponding supergravity solutions.
Adopting the matrix theory description, we construct the worldvolume gauge
theories and prove the absence of any tachyonic degrees. We also study
supersymmetric solitons of the worldvolume theories.
