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The information presented in this cross reference is based on TOSHIBA's selection criteria and should be treated as a suggestion only. Please carefully review the latest versions of all relevant information on the TOSHIBA products, including without limitation data sheets and validate all operating parameters of the TOSHIBA products to ensure that the suggested TOSHIBA products are truly compatible with your design and application.
Please note that this cross reference is based on TOSHIBA's estimate of compatibility with other manufacturers' products, based on other manufacturers' published data, at the time the data was collected.
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典型运算放大器的开环增益约为105(100dB)。如果没有反馈,由于高增益灵敏度,运算放大器会给电路设计带来困难。负反馈可将增益和截止频率设为预期值,从而提高稳定性并减少性能变化、部件之间的变化以及对温度和其它环境参数的灵敏度。
图1显示了反相放大器。此负反馈电路的闭环增益(Gv)可简单地用下式表示:
Gv=-R2/R1
此公式表明闭环增益仅由外部电阻比决定,而不受环境因素的影响。
图2显示了典型运算放大器的波特图。开环增益(即无负反馈的增益)按6dB/oct(=20dB/dec)的速率减小。相反,闭环增益在此图中具有从DC至10kHz的恒定增益(取决于运算放大器的频率响应)。如本例所示,可使用反馈为放大器提供带宽。
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