原创 一个关于运放SR（压摆率）的问题

一个关于运放SR（压摆率）的问题

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http://www.analogcn.com/Article/wz2/200701/20070126235007.html

问：个4hz,10mv信号通过带通放大器放大时，发现输出信号幅度和相位都不稳定，那么是放大器有问题还是那个信号本身不稳定？

  [答：Eagle]The slew rate (SR) of an amplifier is the maximum rate of  change of voltage at its output.

        It is expressed in V/s (or, more probably, V/μs). It"s test when give a step voltage input.

        It will affect full power band width. FPBW = Slew Rate/2πVp. If you signal is small, then the normal band width (small signal band width) ok. If signal is large, it"s limited by slew rate.

       It depends on your phase margin, you need reserve 30" phase margin.

       Normallly  capacitor load will reduce phase margin, you can add a small resistors serially connect with CAP when you use a big capacitor. If the signal is 4 HZ only,  I think a low pass filter is OK. Please do not use high gain at filter stage. Suggest one gain stage with a low offset low drift amplifier such AD8662 or OP2177 (60uV offset, 0.7uV/"C drift) at gain stage, then use another stage  as filter.

       Another way to remove offset effect of an amplifier is use AC copler, then it"s will be band pass with another low pass filter stage.