| 摘要 |
PURPOSE: A circuit for controlling screen size is provided to doubly control a screen size of a monitor according to a horizontal frequency and a brightness of a screen. CONSTITUTION: A signal amplitude controller(100) includes the first variable resistor(R1) for increasing and decreasing amplitudes of the first and second voltage signals from a horizontal deflection circuit(10) and a high voltage generating circuit(30), respectively. A signal inverse flow preventing section(300) includes the first and second diodes(D1,D2) for preventing inverse flows of the second and first voltage signals, respectively. A buffer(500) includes an IC(A1) having a non-inverting terminal and an inverting terminal, the first voltage dividing resistor(R3) connected to the non-inverting terminal of IC(A1), the second and third voltage dividing resistors(Ra,R4) connected to the inverting terminal thereof, and a gain control resistor(Rf). A frequency discriminating section(700) includes a resistor(R5) connected to the third voltage dividing resistors(R4) in parallel and a frequency discriminator(50) connected to the resistor(R5).
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