| 摘要 |
PURPOSE:To obtain an AGC circuit very resistant to a strong input and having a large attenuation factor by utilizing the excellent characteristic of a push-pull circuit and a differential amplifier circuit to constitute this circuit. CONSTITUTION:Transistors (TRs) 4 and 5, 6 and 7, and 8 and 9 constitute respectively the 1st, end and 3rd push-pull circuits. The TRs 4 and 6, 5 and 7 corresponding in the 1st and 2nd push-pull circuits are connected differentially respectively to constitute the differential amplifier circuits and the TRs 8, 9 of the 3rd push-pull circuit are connected in opposite phase to the TRs 4, 5 corresponding to the 1st push-pull circuit. A secondary side 1S of an antenna tuning coil 1 is connected between bases of the TRs 4 and 5 and a +B power supply is applied to each collector. The 1st tuning circuit 10 of a high-frequency amplifier stage being the next stage is connected to the emitter of the TRs 6, 7 and the 2nd tuning circuit 11 is connected between the collectors of the TRs 6, 7 respectively. |
