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The Need
This slide shows where noise can be introduced during the amplification step for OpAmp devices. The top block diagram shows a typical flow chart from sensor to AD converter of a MCU or similar applications processor. The first point of noise that can be introduced between the sensor device itself and the OpAmp amplifier is the OpAmp’s Input Bias Current. This can also be considered as an error factor in the output voltage/current of the sensor itself when compared to the circuit using the amplifier. The next point of noise occurs at the output of the OpAmp and is typically indicated as input offset voltage errors. This often looks like a shift in the output DC voltage when amplifying at a high amplification factor. This presents an error when the upper voltage levels saturate and become unable to represent the high peaks of the signal as shown in the middle picture. Finally, the last point of noise that can occur during OpAmp amplification is related to the input referred noise voltage density. This is also related to the AC voltage error of the OpAmp and looks like noise on the output signal. Again, this error also occurs when boosting a signal with high amplification factors. This presentation will introduce the CMOS OpAmp which is a solution for these points of noise.
PTM Published on: 2019-01-23