| 摘要 |
PURPOSE:To eliminate the noise contained in the input signal, by providing a transistor in which an output is extracted out of the collector, comparing the emitter voltage of the transistor with the reference voltage and breaking the transistor with the output of comparison. CONSTITUTION:The emitter voltage of a transistor TRQ1 is compared with the reference voltage V5 in order to eliminate the noise pulse superposed on a composite video signal V1. The output of this comparison is supplied to the base of a TRQ2 with the emitter grounded, and the TRQ1 is broken by the output of comparison. The voltage lower than the bias voltage V4 by an amount equivalent to the base-emitter voltage of the TRQ1 is set equal to the synchronous tip voltage of the signal V1. Then the self-biasing is carried out for the emitter of the TRQ1. As a result, a comparator A works to make the TRQ2 conduct. Thus the base voltage of the TRQ1 is set nearly at 0V, and the TRQ1 is broken. |
