DIRECT CURRENT REPRODUCING CIRCUIT

摘要

PURPOSE:To execute essentially the direct current reproduction and to prevent the difference of the luminance between the beginning and the end of the horizontal synchronization by sample-holding a black signal area immediately after the synchronizing signal and obtaining difference signal between the input signal and the sample-held voltage. CONSTITUTION:An alternating current linked input signal (a) is inputted from a terminal 5. The input signal (a) is inputted to the positive phase input of a synchronizing detecting circuit 1, a sample and hold circuit 3 and a differential amplifier 4. A horizontal synchronizing signal (b) is outputted from the synchro nizing detecting circuit 1. The horizontal synchronizing signal (b) is converted to a pulse signal (c) of a constant width DELTAt later than the horizontal synchroniz ing signal by a pulse forming circuit 2. Based on the pulse signal (c), the sample and hold circuit 3 sample-holds the input signal (a). The difference signal be tween the holding voltage and the input signal (a) is outputted by the differential amplifier 4. The voltage to be sampled is a black level reference voltage, and the stable voltage can be obtained.