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发明授权
CN101026359B 运算放大器 失效 - 权利终止

运算放大器
摘要：
根据本发明的实施例的运算放大器包括：控制信号输入端，从外部设备接收数字控制信号；第一和第二晶体管，作为差分放大器电路的差分对；恒流电路，将预定电流提供给差分对；在恒流电路和第一晶体管间提供并生成第一电位差的第一电阻器；以及在恒流电路和第二晶体管间提供并生成第二电位差的第二电阻器，运算放大器根据输入到控制信号输入端的控制信号，改变第一电阻器和第二电阻器间的电阻值比。
摘要（英）：

An operational amplifier according to an embodiment of the invention includes: a control signal input terminal receiving a digital control signal from an external device; first and second transistors as a differential pair of a differential amplifier circuit; a constant current circuit supplying a predetermined current to the differential pair; a first resistor provided between the constant current circuit and the first transistor and involving a first potential difference; and a second resistor provided between the constant current circuit and the second transistor and involving a second potential difference, the operational amplifier changing a resistance value ratio between the first resistor and the second resistor in accordance with the control signal input to the control signal input terminal.

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