PURPOSE: To improve the fluctuation of the vertical amplitude caused by the anode voltage (high voltage) of a CRT with a vertical deflecting circuit of a TV receiver or a display monitor, etc.

CONSTITUTION: A correction voltage generating circuit 3 generates a 2nd signal 13 only in a small current area of an anode current Ia based on a 1st signal 12 received from an anode current detecting circuit 2. The signal 13 is applied to a sawtooth waveform generating capacitor C1 via a resistance R1. Thus the amplitude of the both-end voltage of the capacitor C1 increases with reduction of the current Ia and then reduces with increase of the current Ia. Then the vertical amplitude is increased for the former case and reduced in the latter case respectively. The signal 13 is not outputted in the areas where the current Ia is kept at a prescribed level or higher and therefore the vertical amplitude is not corrected.