[en] A new mechanism of the negative differential conductivity (NDC) effect in semiconductor superlattices (SL) is proposed and analysed that is due to the conduction electron trapping by donor centers. It is shown that the NDC effect occurs for sufficently high (but reasonable) impurity concentration and not too large value of the τ_ε/τ_c ratio (where τ_ε is the electron energy relaxation time and τ_c the electron life time in the conduction band) when the applied d.c. electric field reaches certain critical value defined by the physical parameters of the sample. (author). 8 refs, 2 figs