[chapter] Low-Voltage Analog IC Design

Deepika Gupta¹

Low-Voltage Analog Integrated Circuit Design

Nanoscale VLSI. Book series (ESIEE) (2020) pp 3-22

DOI: 10.1007/978-981-15-7937-0_1

¹Department of Electronics and Communication Engineering, IIIT Naya Raipur, India

Abstract: In this chapter, we review the challenges and effective design techniques for ultra-low-power analog integrated circuits. With the miniaturization, having low-power low-voltage mixed signal IC is essential to maintain the electric field in the device. This constraint presents bottleneck for the researchers to design robust analog circuits. Specifically, the low value of supply voltage with small technology influences many specifications of analog IC, e.g., power supply rejection, dynamic range and immunity to noise, etc. In addition, it also affects the ability of the MOS transistor to be operated in the strong inversion region. Note that with the technology reduction, power supply VDD is reducing but the threshold voltage VT is not decreasing proportionally to maintain low leakage current. However, this process reduces the overdrive voltage and limits the staking of transistors. In this case, the transistor can be made to work in weak inversion to work and reduce the power consumption. Further, reduction in VDD to achieve low-power consumption causes many other circuit-related issues such as PVT variations, degradation of dynamic range, mismatching in circuits element and differential paths. There have been many design methods developed for the ultra-low-power analog ICs. In this chapter, we will discuss some of the design techniques to reduce the power consumption in analog ICs. In addition, we will also discuss the basic building blocks of analog circuits with discussed design techniques. The charge-based EKV model can be a very suitable example of a MOS simulation model to be used in all inversion regions of transistor operations [Enz 2017]. In EKV model, the smallest number of core parameters is needed for the accurate behavioral modeling of transistor. Particularly, charge-based EKV model is beneficial for the analysis of analog circuits because it allows the analysis with simple calculations over different inversion regions. Hence, developing new device simulation models specific for analog circuit design is crucial.

Fig: Vth and Vdd scaling trend vs. Leff  [Zhao 2006]

References:

[Enz 2018] Enz C, Chicco F, Pezzotta A (2017) Nanoscale MOSFET modeling-part 1: the simplified EKV model for the design of low-power analog circuits. IEEE Solid-State Circuits Magazine 9(3):26–35

[Zhao 2006] Zhao W, Cao Y (2006) New generation of predictive technology model for sub-45 nm early design exploration. IEEE Trans Electron Devices 53(11):2816–2823