[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

[paper] Low-voltage, Non-volatile, Compound-semiconductor Memory Cell

Room-temperature Operation of Low-voltage, Non-volatile, Compound-semiconductor Memory Cell

Ofogh Tizno, Andrew R. J. Marshall, Natalia Fernández-Delgado, Miriam Herrera, Sergio I. Molina
and Manus Hayne

Scientific Reports volume 9, Article number: 8950 (2019) 

DOI: 10.1038/s41598-019-45370-1

Abstract: Whilst the different forms of conventional (charge-based) memories are well suited to their individual roles in computers and other electronic devices, flaws in their properties mean that intensive research into alternative, or emerging, memories continues. In particular, the goal of simultaneously achieving the contradictory requirements of non-volatility and fast, low-voltage (low-energy) switching has proved challenging. Here, we report an oxide-free, floating-gate memory cell based on III-V semiconductor heterostructures with a junctionless channel and non-destructive read of the stored data. Non-volatile data retention of at least 10000s in combination with switching at ≤2.6 V is achieved by use of the extraordinary 2.1 eV conduction band offsets of InAs/AlSb and a triple-barrier resonant tunnelling structure. The combination of low-voltage operation and small capacitance implies intrinsic switching energy per unit area that is 100 and 1000 times smaller than dynamic random access memory and Flash respectively. The device may thus be considered as a new emerging memory with considerable potential.

FIG: Device structure a) Schematic of the processed device with control gate (CG), source (S) and drain (D) contacts (gold). The red spheres represent stored charge in the floating gate (FG). b) Cross-sectional scanning transmission electron microscopy image showing the high quality of the epitaxial material, the individual layers and their heterointerfaces.

Simulation Methods: The nextnano software package was utilised for mathematically modelling the energy band diagram of the memory device structure reported here, taking into account strain and piezoelectricity. Within this work, a self-consistent Schrödinger solver was used along with the Poisson and drift–diffusion equations to calculate the electron densities at equilibrium and under bias.

[paper] Design techniques for low-voltage analog integrated circuits

Matej Rakus, Viera Stopjakova, Daniel Arbet

Institute of Electronics and Photonics, Faculty of Electrical Engineering

and Information Technology Slovak University of Technology in Bratislava, Slovakia,

Journal of ELECTRICAL ENGINEERING, Vol.68 (2017), No.4, 245–255

DOI: 10.1515/jee-2017–0036

ABSTRACT: In this paper, a review and analysis of different design techniques for (ultra) low-voltage integrated circuits (IC) are performed. This analysis shows that the most suitable design methods for low-voltage analog IC design in a standard CMOS process include techniques using bulk-driven MOS transistors, dynamic threshold MOS transistors and MOS transistors operating in weak or moderate inversion regions. The main advantage of such techniques is that there is no need for any modification of standard CMOS structure or process. Basic circuit building blocks like differential amplifiers or current mirrors designed using these approaches are able to operate with the power supply voltage of 600 mV (or even lower), which is the key feature towards integrated systems for modern portable applications.

Fig: Parameter gm/ID versus the normalized drain current. MOS transistor operates in weak inversion (WI) for i_c < 0.1. Strong inversion (SI) is for i_c < 10. Everything in between belongs to the moderate inversion (MI) with center in i_c = 1