| 摘要 |
<p>RCA 72,717 A protection circuit for limiting the power dissipation of a video output amplifier when high frequency signals of significant magnitude and with a high density of occurrence (e.g., noise during vacant channel reception) are supplied to the amplifier. The protection circuit includes a control transistor and a sensing network. The sensing network monitors a video signal coupling path to detect the presence of high frequency signals, and derives a voltage representative thereof. The derived voltage is insufficient to render the control transistor operative under normal signal conditions. Under abnormal conditions when significant amounts of high frequency signals with a high density of occurrence are present, the derived voltage is sufficient to render the control transistor operative to develop an output control voltage. The control voltage is applied to the video signal path so as to attenuate the signal including the high density components, such that excessive conduction and power dissipation of the amplifier in response to the high density components is limited.</p> |
