| 摘要 |
PURPOSE:To avoid the erroneous detection of signal in case a detecting signal is obtained by giving the full-wave rectification to the output of a differential amplifier, by turning off a full-wave rectifying circuit when the output voltage to be supplied to the differential amplifier is equal to the reference level. CONSTITUTION:A differential amplifying circuit consists of the transistors TR1 and TR2, and a full-wave rectifying circuit 10 consists of a TR11 and TR12. The joints between the emitters and bases of the TR11 and TR12 are connected to the collectors of the TR1 and TR2. Then an output is obtained from a joint between the collectors of the TR11 and TR12. A reference voltage setting circuit consisting of a series circuit of a resistances 7 and 8 plus a variable resistance 9 is connected to the base of the TR2. The TR1 and TR12 are turned off when the signal voltage to be supplied to the base of the TR1 is at the reference level. In such a way, an erroneous output can be prevented. |
