| 摘要 |
PURPOSE:To suppress the variance of gain caused by the variance of a value of resistance of an integrated circuit, by providing an error amplifying for comparing the same phase output voltage and a reference voltage, detecting an error from a prescribed value of a current quantity of a constantcurrent source, and executing a negative feedback control so that said current quantity becomes the prescribed value. CONSTITUTION:The same phase output voltage detecting resistances 14, 15 which have eliminated a constant-voltage source in a conventional circuit, and in which a constant-voltage source 16 and one end are connected to an output terminal 4 and 5, respectively, and the other end is connected in common at a point A, and an error amplifier 17 in which an inversion input is connected to the constant-voltage source 16, and a non-inversion input is connected to the point A, and an output is connected to a base of a transistor 8 are added. In this case, a resistance value RA of the resistances 14, 15 is higher enough than a resistance value RL of resistances 11, 12. A voltage of the connecting point A is a voltage which has divided a voltage of output signals whose phases are opposite to each other, into two, and becomes equal to the same phase output voltage of a differential amplifying circuit. The potential of the point A is compared with a reference voltage VR, and by an output of the error amplifier 17 corresponding to its difference, the base of the transistor 8 for constituting a constant- current source is biased. By this operation, with regard to the constant-current quantity of the constant-current source, a negative feedback control is executed as a circuit.
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