| 摘要 |
PURPOSE:To prevent oscillation due to the change of element characteristics and to prevent the increase of nonlinear distortion of a negative feedback amplifier by subtracting a negative feedback signal from an inputted signal and attenuating the subtraction output by the quantity of attenuation designated by a control signal. CONSTITUTION:The difference between an input signal 10 from an input terminal 101 and a negative feedback signal 4 from a fixed attenuator 140 is inputted from a comparator 110 to a variable attenuator 120, and the output is amplified by an amplifier 130 and is outputted to an output terminal 102. A part of an output 3 from the terminal 102 is applied to the attenuator 140 for open-loop gain adjustment, and the output is supplied to the comparator 110 as a signal 4. The quantity of attenuation in the variable attenuator 120 is determined by monitoring a DC current supplied from a power source 160 to the amplifier 130 and is applied to the variable attenuator 120 as a control signal 5. Oscillation of the amplifier is prevented even in case of the change of electronic characteristics from designed those, and the increase of non-linear distortion is prevented.
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