| 摘要 |
PROBLEM TO BE SOLVED: To obtain an inexpensive dynamic focus circuit where no focus deviation is caused even when a deflection width is changed. SOLUTION: The dynamic focus circuit is provided with at least an FBT 1 that generates a high DC voltage to apply a dynamic focus(DF) signal to a grid terminal of a CRT, a coupling capacitor C1 that uses a breeder resistor to divide the high voltage so as to obtain a bias voltage suitable for the CRT and superimposes an AC waveform of the DF signal on the bias voltage, a DF amplifier 2 that outputs the DF signal with a large amplitude suitable for the CRT to the coupling capacitor C1, and with a DC correction circuit 4 that controls a voltage at a ground level side of the breeder resistor so as to obtain the proper bias voltage at the grid terminal on the basis of the DF signal from the DF amplifier 2.
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