| 摘要 |
PURPOSE:To stabilize the detecting operation by applying AM detection by means of transistors (TR) and providing a special amplifier between said TRs and an intermediate frequency amplifier so as to apply circuit integration to the AM detection circuit incorporatedly with the intermediate frequency amplifier. CONSTITUTION:An opposite phase intermediate frequency signal is extracted from a differential amplifier 1 at the final stage of the intermediate frequency amplifier comprising TRs Q1, Q2 and amplified by a differential amplifier. Then the intermediate frequency signal is subjected to TR detection by TRs Q3, Q10. In this case, since an opposite phase intermediate frequency signal is fed to the TRs Q3, Q10 to each other, the detection acts like full-wave rectification and the detected output includes the 2nd order carrier frequency component and its harmonics only. Thus, the capacitance of a capacitor C3 is decreased and circuit integration is attained. Further, the pre-stage of TRs Q9, Q10 is constituted as the balanced type, negative feedback is applied to TRs Q4, Q5, and the TRs Q9, Q10 are coupled directly, then the operating point is balanced stably at all times.
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