| 摘要 |
PURPOSE:To prevent the influence of a time constant upon a differentiating means during speeding-up operation by decreasing the time constant of a time constant circuit by a differential output of pulses when channel-selection driving pulses are inputted, and then resetting that by the output of the time constant circuit. CONSTITUTION:A channel-selection driving pulse when inputted to an input terminal 1 or 2 is differentiated by a differentiating means 57, whose output is applied to an FF61. As a result, the FF61 operates to turn on a transistor TR4, short-circuiting a resistance 26. Then, a line 23 is charged with a time constant determined by a resistance 65 and a capacitor 24. When the potential of the line 23 rises, a bistable circuit 34 turns on and the capacitor 24 is discharged to lower the potential of the line 23. In this case, the trailing edge of a voltage is differentiated by a differentiating means 66, whose output is applied to the FF61. As a result, the output of the FF61 is inverted to turn off the TR64, and the capacitor 24 is charged through a resistance 26, thus increasing the time constant. |
