Complex sentence: Dependent sources are useful, for example, in modelling the behavior of amplifiers; a biolar junction transistor can be modelled as a dependent current source whose magnitude depends on the magnitude of the current fed into its controlling base terminal.
Split into simpler sentences: Dependent sources are useful, for example, in modelling the behavior of amplifiers. A bipolar junction transistor can be modelled as a dependent current source whose magnitude depends on the magnitude of the current fed into its controlling base terminal.