A dynamic focus amplifier for generating a dynamic focus voltage for a
focus electrode for a cathode ray tube at a capacitive load includes a
source of a periodic signal at a horizontal deflection frequency. A
pull-down transistor is responsive to the periodic signal and coupled to
the capacitive load 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 is coupled to the capacitive load for replenishing a charge
stored in the storage capacitor from a charge stored in the capacitive
load to develop a control voltage in the storage capacitor. A pull-up
transistor is responsive to the control voltage and coupled to a source
of a high voltage and to the capacitive load 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.