| 摘要 |
PURPOSE:To improve the accuracy by providing a connection element between an output node and an output terminal in two differential amplifier circuit and connecting an inverting input of each differential amplifier circuit to the output terminal so as to suppress the variation of the gain of each differential amplifier circuit. CONSTITUTION:The addition ratio of an analog signal A at an input terminal 1 to an analog signal B at an input terminal 2 is the ratio of gain in the 1st and 2nd differential amplifier circuits 4, 14. The differential amplifier circuits 4, 14 have the same gain, except one differential amplifier cicuit, e.g., the amplifier circuit 14, a base of a transistor (TR) 9 is not connected to an output terminal 3, and when a DC bias is given, a voltage difference between a base potential of a TR 5 and a base potential of the TR 9 is amplified and outputted at an output terminal 3, and the gain in this case is referred to as G0. In this circuit, when the base of the TR 9 is not connected to the DC bias but connected to the output terminal 3 and an output is fed back, the gain G1 is 1/(1+1/G0), and even when the gain G0 is fluctuated by nearly 5% due to the variation of components based on the circuit integration, the gain G1 has nearly 0.3% only in the fluctuation.
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