Raster distortion correction circuit

A deflection apparatus with raster distortion correction comprises a horizontal deflection circuit generating an S-shaped deflection current, and a modulation circuit with a resonant circuit producing a modulation current (I M ). That modulation current (I M ) modulates a voltage (U CS ), developed in an S-capacitor (C S ) in accordance with a vertical modulation signal (S V ). By producing the modulation current (I M ) a switching semiconductor (Q M 4) of the resonant circuit has a first switching state during a first portion of the trace interval and a second switching state during a second portion of the trace interval. The first and second portions varies as a result of a pulse-width modulator (O M 5), which is responsive to the modulation signal (S V ) and to a feedback signal for controlling the switching semiconductor (Q M 4) in a negative feedback closed loop. A feature of the present invention is to use the voltage (U CS ) developed in the S-capacitor (C S ) as the feedback signal.