| 摘要 |
PURPOSE:To attain low offset current, high speed addition and miniaturization and circuit integration by applying on offset current of a common base transistor (TR) for addition from a constant current source connected to an input section so as to attain the constitution by NPN TRs only. CONSTITUTION:A TR 10 is of common base type and forms a Miller circuit with a diode 9 and an emitter potential is brought nearly into a common potential by making a current value of a constant current source i2 nearly coincident with a collector current of the TR 10. The emitter of the TR is connected to two input currents and a constant current source 12, one of the input currents is an output current i2 of a DA converter 2 and the other is a conversion of the input current i1 by dividing the input voltage signal e1 by a resistor R1, then the constant current source I1 is selected larger than the input current level. In selecting properly a resistance value R2, the added input is amplified to an optional value and the DC voltage drop by the resistor R2 is decreased by setting the constant current source I1 to a comparatively smaller value. Thus, the operating current is decreased, the low power consumption and miniaturization of TRs and resistors are attained.
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