| 摘要 |
PURPOSE:To constitute simply a circuit capable of decreasing the variation in a gain between different bands such as VHF and UHF by constituting the 1st and 2nd switches so that one switch is operated when the other is closed, selecting a signal of a band and applying the signal to a mixer of the next stage. CONSTITUTION:A current flows to a transistor (TR)Q2 from a switching power supply Bu through a choke coil L2 and a switch diode D3 at the receiving of UHF. The diode D3 is turned on in this case. A UHF signal is applied to the 1st gate G1 or a TRQ1 through a coupling capacitor C3 from the cross point of the diode D3 and the coil L2. On the other hand, the switching power supply Bu is a negative potential at the receiving of VHF and the switch diode D3 and the TRQ2 are cut off, then only the VHF signal is applied to a gate G1 of the TRQ1. Thus, an input signal is given to the amplifier of the 2 stages comprising the TRs Q1, Q2, allowing to improve the gain of UHF. |
