[en] Theoretical study of the transport properties of semiconductor superlattice (SL) in the presence of external electric field E(t) has been investigated with the help of Boltzmann's equation. The model adopted agrees fairly well with experimental work as well as Monte Carlo simulation. Among the phenomena observed are the induced self transparency, absolute negative conductivity and the negative differential conductivity. In the case of negative differential conductivity (NDC) it is observed that it does also occur under the a.c. and d.c electric field but appears only when ωτ << than 1. It does appear in the vicinity where the d.c field E₀ is equal to the amplitude of the a.c. field E₁ and the peak decreases with an increase in E₁. (author). 20 refs, 1 fig