Plasmons in two-dimensional electron channels have
potential applications in the terahertz frequency
range. Equivalent circuit models provide a convenient
framework for analysing the plasmons. This paper
introduces a circuit model for plasmons in the
presence of a dc current that flows in a gated channel.
It is shown that drifting plasmons can be descried by
an LC-transmission line with distributed dependent
sources. A circuit analogue of the Dyakonov-Shur
instability is demonstrated. Then, a lumped-element
transmission line with dependent sources is analysed,
and non-reciprocity is demonstrated for examples of
a right- and left-handed transmission lines. Effects
of Ohmic loss are discussed. The results could be
used for the design of non-reciprocal transmission-
line devices.