▎ 摘　　要

The amplification of terahertz electromagnetic radiation in a structure with two layers of graphene through which a direct electric current flows is studied theoretically. The hydrodynamic conductivity of graphene is investigated. It is shown that the real part of the graphene conductivity can be negative in the terahertz-frequency range at the drift velocities of charge carriers in graphene that are lower than the phase velocity of an electromagnetic wave. For small wave vectors of a terahertz wave that is incident on a graphene structure, the spatial dispersion insignificantly contributes to the hydrodynamic conductivity of graphene. Due to this, the amplification efficiency does not depend on the direction of currents in each of the graphene layers. It is shown that graphene with a direct electric current can be used to create terahertz amplifiers operating at room temperature.