| 摘要 |
A dynamic focus amplifier (17) for generating a dynamic focus voltage for a focus electrode for a cathode ray tube (12) at a capacitive load (C602, C wire, CTl) includes a source of a periodic signal at a horizontal deflection frequency. A pulldown transistor (Q1) is responsive to the periodic signal and coupled to the capacitive load (C602, C wire, CTl) for producing, in accordance with the periodic signal, a first portion of the dynamic focus voltage that decreases, during a first portion of a period of the periodic signal. A storage capacitor (C501) is coupled to the capacitive load (C602, C wire, CTl) for replenishing a charge stored in the storage capacitor (C501) from a charge stored in the capacitive load to develop a control voltage in the storage capacitor (C501). A pull-up transistor is responsive to the control voltage and coupled to a source of a high voltage and to the capacitive load (C602, C wire, CTl) for producing from the high voltage a current that is coupled to the capacitive load. The current develops a second portion of the dynamic focus voltage that increases, during a second portion of the period of the periodic signal, and stores the charge in the capacitive load (C602, C wire, CTl). |
