| 摘要 |
PURPOSE:To make a size constant irrespective of brightness of a picture by changing the magnitude of vertical deflection current by voltage corresponding to the beam current of a cathode ray tube. CONSTITUTION:When the brightness of a picture increases and a beam current increases, voltage drop of a resistor 11 becomes larger. This voltage is led through the buffer of a Tr22 and utilized. The voltage obtained in the emitter of the Tr22 is regulated by resistors 20 and 19 and fed to an N-FET18 gate. Thus, when the brightness of picture changes, the gate voltage of the FET18 changes and the resistance between drain sources changes. At it is connected to the feedback path of an IC for vertical oscillation pre-amplification 16 through a condenser 17, saw tooth voltage for feedback AC changes with the brightness of the picture. For instance, when a picture becomes brighter, feedback saw tooth wave components becomes larger, and the vertical deflection current becomes smaller. |
