| 摘要 |
PURPOSE:To perform a channel shift even when the width of a channel selection driving pulse is short, by providing a channel shift start speeding-up circuit. CONSTITUTION:When channel selection driving pulses are supplied to input paths 1 and 2, diodes 49 and 50 turn on to cause a voltage drop across a bis resistance 55, so a transistor 53 turns on to charge a capacitor 24. Since the value of a resistance is small, the cahrging time constant of the capacitor 24 is extremely small during this period. As the channel selection pulses are ceased, the diodes 49 and 50 turn off and a current flows from a power source line 25 through resistances 56 and 51 to a capacitor 54, which is discharged. For this purpose, the resistance 54 of a speeding-up circuit 48 is set much less than the resistance 26 of a time constant setting circuit 5, so that driving is enabled even when the channel selection driving pulses have extremely short width. |
