4. Amplification

For the noise-limited ADC, in order to achieve high SNR, the residue amplification is normally required to amplify the conversion residue and improve the accuracy. First, three approaches of residue amplification are presented, and they are opamp-based amplification, comparator-based amplification, and open-loop dynamic amplifier. Since the opamp-based amplification still plays a critical role in the data conversion, we talk about how to provide an opamp for a low-power and high-performance ADC in the following sections. On one hand, we focus on the circuit techniques that assist in relaxing the requirements of the opamp. On the other hand, the opamp design is depicted and a hybrid opamp is introduced in detail. At the end of the chapter, we sum up the residue amplification for the power-efficient and high-performance ADC.