Abstract: Reductions in size and cost for a sync chip clamping/sync separation circuit are envisaged by the use of the CMOS process. The final output amplification section of a differential amplifier circuit is implemented as a P channel FET, and the pull down current for the drain terminal of this P channel FET is set to a value which is smaller than the current which flows when this P channel FET is ON. A constant voltage is supplied by resistors to the non inverting input terminal (+) of the differential amplification circuit. Further, the inverting input terminal (-) of the differential amplification circuit and the output terminal thereof are connected, and also an input coupling capacitor is interposed between the inverting input terminal (-) thereof and an video signal input terminal. Further, a buffer is provided which takes out a sync signal from an input of the P channel FET.

Abstract: In a ring oscillator type VCO in which plural stages of inverter circuits are cascade-connected to each other so as to constitute a positive feedback loop, delay amounts for both a rising edge and a falling edge of an output signal from the inverter circuit are controlled to have the same delay amount by way of a control signal. These delay amounts of the rising edge and the falling edge are controllable in such a manner that the duty ratio of an oscillator output signal is not varied. Each stage of the inverter circuit is arranged by three-stage inverters made of load transistors and driver transistors, and the control voltage is applied to the load transistors of the two adjoining inverters among the three-stage inverters.