| 摘要 |
PURPOSE:To switch the mode automatically to the stereo reception mode when no SAP signal exists by adding a switching circuit comprising two transistors (TRs). CONSTITUTION:When an SAP detection circuit 36 detects no SAP signal, a TR 1 forming a switching circuit is turned on and a TR 2 is turned off. Thus, a current mirror circuit comprising TRs 3,4 is not activated. Thus, no current is fed to the switching circuit comprising the TRs 5, 6, a voltage at an SAP mode switching voltage output terminal 19 is fixed to a low level and independent of on/off of the switch 21. On the other hand, the input of the current mirror circuit comprising TRs 9, 10 is connected to a collector of the TR 1, then the TR 9 is turned on and activated to bring the potential at a stereo mode switching voltage output terminal 20 to a high level.
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