The traditional power meter calibrating system usually has the shortcomings of low efficiency and large volume due to its standard voltage and current source rely on the analog amplifier.
传统的电力校表台由模拟功放向待校电表及标准表提供校表电流，造成系统效率低、体积大、重量重。
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An OPA128 operational amplifier with extreme low bias current and big gain is adopted for enhancing the response to weak signals.