| 摘要 |
PURPOSE:To remove the generation of an unnecessary output at the time of no input by supplying idling current to the signal input side of a differential amplifier by a constant current circuit to which operating current common to the differential amplifier is applied. CONSTITUTION:Since current corresponding to a half of current flowing into a Tr8 of the differential amplifier 2 is made to flow into Trs 4, 6, the value of current applied from a Tr56 of the constant current circuit 48 to the Tr6 is set up to 1/2hFE under the consideration of current amplification factor hFE, so that the emitter area of the Tr54 is set up to twice the Tr56. Consequently, constant idling current 1/2hFE is applied to the base of the Tr6 independently of the existence of the signal input and the base bias of the Tr6 is increased, so that no output is generated until a signal is applied to an input terminal 26.
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