| 摘要 |
<p>There is provided a switching circuit of a BS converter capable of assuring a high sensitivity. A BS tuner (1) superimposes a band switching pulse signal on a power voltage when selecting a high band, and supplies the resulting signal to a BS converter (4). The BS converter (4) amplifies a pulse signal selected by a filter circuit (11) of a switching circuit (9) by ten times in a differential amplifier (12), rectifies the resulting signal in a rectifying circuit (13), and compares the resulting signal with a reference voltage in a comparator circuit (14), thereby detecting the presence or absence of the band switching pulse signal. When the band switching pulse signal is detected, a high-band local oscillator (16) is turned on by a drive circuit (15). When the signal is not detected, a low-band local oscillator (17) is turned on. Thus, by amplifying by about ten times the band switching pulse signal having a voltage of about 0.6 V, a reception frequency band is switchedly selected with high accuracy. <IMAGE></p> |
