Broadband opamps for multi-channel communication systems have strong demands on linearity performance. When these opamps are integrated in deep sub-micron CMOS technologies, the signal-swing has to occupy a large part of the rather low supply voltage to maintain the signal-to-noise-ratio. To obtain opamps with low distortion it is necessary to do a thorough analysis of the nonlinear behaviour of such circuits and this is the main subject of Design Criteria for Low Distortion in Feedback Opamp Circuits.

The biasing of each transistor in the circuit is a major issue and is addressed in this work. It is important to bias the transistor such that the distortion is low and stable in the entire range of its terminal voltages. This will ensure high linearity and robustness against variations in circuit conditions such as power supply voltage, bias current and process variations.