| 摘要 |
PURPOSE:To make the amplitude of a sawtooth wave constant regardless of the frequency of a synchronizing signal by detecting the duty ratio of a sawtooth wave generating circuit and feeding back the detection output of the duty ratio so as to vary the charging current of an integration circuit of the sawtooth wave generating circuit. CONSTITUTION:The output of an operational amplifier 10 is integrated by the integration circuit comprising a resistor 15 and a capacitor 16. Since the high level voltage of an operational amplifier 10 is 2Vr, when the duty ratio of the output of the operational amplifier 10 is 50%, the integration level becomes the voltage Vr. An output voltage -Vc of the amplifier 17 is at a level lower than the voltage -Vr fed to an operational amplifier 1. When an output voltage -Vc of the operational amplifier 17 rises, the potential difference with the voltage -Vr fed to the operational amplifier 1 is small, a current i1 flowing via a resistor 21 is decreased and the charging current flowing to a capacitor 5 is decreased. the charging current flowing to the capacitor 5 is subject to feedback control so as to be equal to the voltage fed to the input terminal and the amplitude of the sawtooth wave outputted from the terminal 8 is made constant. |
