In order to explain to the engineer how a Current Sense Amplifier (CSA) is different than a typical operational amplifier this slide looks at key specifications for the 36 V MAX44284 CSA and the MAX44241 which is a 36 V, ultra-precision, low-noise, low-drift, single operational amplifier. Current-sense amplifiers magnify a small differential voltage while rejecting the input common-mode voltage. In this role they operate like traditional op amp-based differential amplifiers. There is, however, an important difference between these two amplifier architectures. The input common-mode voltage for current-sense amplifiers is allowed to exceed the power-supply (VDD) voltage. When, for example, the MAX44284 current-sense amplifier is powered from VDD= 5 V, it can still withstand an input common mode voltage of 36 V. By using unique amplifier architectures, current-sense amplifiers are not hampered by the common-mode rejection limitations (CMRR) that arise from mismatched resistors. The MAX44284 for example, has 145 dB (typ.) DC CMRR. In contrast, the performance of traditional op amp-based differential amplifiers is negatively impacted by CMRR, and their effective input VOS is  magnified through the signal chain.