Chopper stabilized low noise CMOS operational amplifier

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Dr. Bognár György
Department of Electron Devices

The purpose of this thesis is to design a low-noise, low-offset CMOS operational amplifier for general use. The amplifier is intended to use in low-frequency systems, where high precision is required rather than high bandwidth.

To achieve low noise and offset, first we must investigate the source of these errors. Therefor in the first part of the thesis I will describe the sources of the amplifiers offset and noise, than I present two design techniques, which techniques offering us a solution to lower or completly eliminate the offset and the low-frequency noise of the amplifier. These techniques are the Autozero technique and the Chopper Stabilization. The principle behind these two techniques will be explained, as well as their limitations, problems.

In the second part of this thesis, I present the designed amplifier due to the design steps. First of all the DC operation will be described, than the frequency compensation of the amplifier. After that the transient behavior will be discussed. The thesis ends with the presentation of the amplifiers noise. During the second part of the thesis I discuss every design step and considerations leading to the optimum design. Considerations of other options to improve parameters will be taken and discussed in the text too.


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