Continuous-time Sigma-Delta ADCs are preferred over Discrete-time Sigma-Delta ADCs for high speed applications. The two famous continuous-time integrator architectures are the opamp-based RC integrator, and the GM-C integrator.
The opamp based RC integrator has better linearity, however it causes resistive loading to the input signal of the ADC, which could add complexity to the buffer driving the signal to the ADC. The GM-C integrator has the advantage of having high input impedance for the input signal. Moreover, the GM-C is used in open-loop condition, hence it could be more suitable for high speed application. However, it suffers from the non-linearity and limited input range.
Goals (extent depending on bachelor or master thesis):
- Design a variety of circuit architectures of the transconductance cell (GM).
- Compare the linearity, input range, noise vs power consumption of the different architectures.
- Explore how the transconductance tuning could be done for every architecture and how this affects the linearity of the GM.
- Explore the variation of the transconductance versus process, temperature and supply variation.
What we expect:
- Good skills in Cadence and knowledge about analog IC design is a must.
- Organized and well documented research and dedication to successful work.