| 摘要 |
PURPOSE:To offer a circuit possible for reducing noises mixed in a chrominance signal and suitable for both recording and reproduction, by providing a circuit for applying respectively side band emphasis and side band deemphasis to a small amplitude input of the chrominance signal at recording and reproduction. CONSTITUTION:In a figure, 7 is a high gain amplifier and 8 is a recording/reproduction changeover switch. A transfer function Gef(a,w) from an input terminal 3 to an output terminal 4 in a system shown in a figure (b), is expressed as an equation I , where Ge(a, w) (a: input amplitude and w: input angular frequency) is a transfer function of an emphasis circuit 5, and A is a gain of the amplifier 7. Thus, when the A is sufficiently larger, the transfer function is described in an equation II, which shows that the characteristic is reverse to that of the emphasis circuit. Then, the system in the figure (b) acts as a deemphasis circuit. In order to use the emphasis circuit in the figure (a) and the deemphasis circuit in the figure (b) in common, a switch 8 is provided to change over the circuit as shown in a figure (c). |
