  The general Dirac equation in 1+1 dimensions with a potential with a
completely general Lorentz structure is studied. Considering mixed
vector-scalar-pseudoscalar square potentials, the states of relativistic
fermions are investigated. This relativistic problem can be mapped into a
effective Schr\"{o}dinger equation for a square potential with repulsive and
attractive delta-functions situated at the borders. An oscillatory transmission
coefficient is found and resonant state energies are obtained. In a special
case, the same bound energy spectrum for spinless particles is obtained,
confirming the predictions of literature. We showed that existence of
bound-state solutions are conditioned by the intensity of the pseudoscalar
potential, which posses a critical value.
