| 摘要 |
<p>The invention discloses a radio frequency switching circuit for VCR. First RF input signals (RF1) which have passed through an antenna are amplified by the collector of an amplifying transistor (P11) of a switchable amplifier (10), and the amplified signals are supplied to an RF output terminal (40). When the amplifying transistor of the switchable amplifier is turned off by a switching control current (I0) (by a modulation voltage), third RF signals (RF3) of the VCR are outputted through the RF output terminal (40) after passing through an output register (R20) of the amplifying transistor. As a result, during the selection of the video channel for the VCR, the introduction of air broadcasting signals are completely blocked. Therefore, the designers do not have to provide vacant channels between the effective channels, and therefore, the designing restraint is freed, while an increase in the number of video channels becomes possible. <IMAGE></p> |
