| 摘要 |
PURPOSE:To improve the performance by applying a signal to a base of a transistor (TR) for a differential amplifier for amplification and extracting the amplified signal to an intermediate frequency filter with no adjustment from one of TRs via an output circuit having a low impedance. CONSTITUTION:A local oscillation signal of a local oscillation circuit is fed to a base of TRs 11, 14 via a resistor 20, a signal fed to emitters of TRs 11, 12 and 13, 14 is switched to extract two signals with opposite polarity to each other subjected to frequency conversion at a connecting point 85 of collectors of the TRs 11, 13 and at a connecting point 86 between collectors of the TRs 12, 14 and they are fed to bases of TRs 31, 32 for differential amplifier via capacitors 17, 18 and amplified. A signal amplified by the collector of TRs 32, 34 is fed to a base of an emitter follower TR 38 and an intermediate frequency signal is extracted at the intermediate frequency filter via a resistor 40 from the emitter of the TR 38. Thus, the intermediate frequency is adjusted with the good S/N and sensitivity. |
