| 摘要 |
An operational amplifier circuit is formed by an operational amplifier stage having a balanced output function and a common-mode feedback amplifier stage. The common-mode feedback amplifier stage includes a first transistor pair which receives a reference voltage at their gates, a second transistor pair having gates connected respectively to a positive and a negative output of the operational amplifier stage, a transistor which receives at its gate an expected operating center voltage, and a current-mirror circuit for feeding-back an output feedback signal to the operational amplifier stage through a feedback path. The common-mode feedback amplifier stage of this invention makes it possible to stabilize the output voltages of the operational amplifier circuit and to enhance or widen an output dynamic range, without an addition of feedback circuit elements which are connected in series to the feedback path and in which voltage drop develops.
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