| 摘要 |
In aspects of the invention, at normal operation, an operational amplifier circuit has feedback applied from the output thereof to the input thereof so that currents equal to each other flow in differential pair transistors, respectively. While, in order that currents equal to each other may flow in the differential pair transistors, respectively, for compensating the difference in threshold voltages in the differential pair transistors, a voltage lower by a certain voltage difference than the voltage applied to the gate terminal of the transistor must be applied to the gate terminal of the transistor. From this, the switching of switches, when a virtual short circuit occurs, can make the output voltage of the operational amplifier circuit become a signal in which positive and negative rectangular ripples, with the values thereof being proportional to the value of the certain voltage difference, are superimposed on a true value.
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