In this paper the importance of correct impedance matching is discussed in dielectrophoresis (DEP) experiments with commercial signal generators. An uncompensated and a 50 Ω terminated setup are compared to an approach utilizing an active in-line buffer with low output impedance. The losses in effective signal amplitude are simulated for different electrode areas with saline fluids. A separation experiment is performed using a single electrode pair with 10 µ m polystyrene microspheres. The separation capability decreases drastically for larger electrode areas for the uncompensated and the 50 Ω terminated setups but proper and constant behavior is found for the active buffer configuration.