1.High-linearity OTA

 

OTAs are one of the most essential building blocks in the signal conditioning chain, they are widely used in instrumentation amplifier, ADCs and etc. To reach high power efficiency, most OTAs employ differential pairs biased in weak inversion. However, the input signal range of such a differential pair is often limited by the linearity of the differential pair, limiting the performance of the system.

 

In this project, we will explore an innovative way to linearize the differential pair for large signals significantly without sacrificing power efficiency.

 

The student will need to:

1.Complete a comprehensive literature review on differential pair linearization techniques

2.Propose an innovative method to linearize the differential pair, without significant penalty on power consumption and chip area.

3.Make a concept-proof schematic design.

4.If feasible, a tapeout will be supported.This concept has been partially verified with an existing design and testbench ready to be used.

 

2.A delta-sigma modulator with area-efficient and/or highly linear floating inverter amplifier (FIA)FIAs are gaining popularity in recent years due to their superior power efficiency. However, they often require a relatively large reservoir capacitor, which occupies a lot of chip area. Meanwhile, its linearity is often limited, restricting the system's performance.In this project, we will explore novel methods to linearize the FIA and/or improve its area efficiency.The student will need to:1.Complete a comprehensive literature review on FIA.2.Propose a method to achieve area efficiency or high linearity.3.Make a concept-proof schematic design.4.If feasible, a tapeout will be supported.This work has a prior art: Y. Liu, X. Wu, Z. Tang, X. Yu, Q. Fan and N. N. Tan, "A 153μW 26nV/√Hz Readout Circuit with BW and Power Scalability Using Capacitively-Coupled Chopper Floating Inverter Amplifier Embedded in a Discrete-Time ΔΣ Modulator," 2024 IEEE European Solid-State Electronics Research Conference (ESSERC), Bruges, Belgium, 2024, pp. 512-515, doi: 10.1109/ESSERC62670.2024.10719533.3.High linearity current sensorHigh-linearity current sensors are needed in high-performance audio and motor systems. Major bottlenecks to achieving high linearity are the self-heating of the current sensing resistor and the voltage-dependency of the sense resistor. These issues can be overcome by selecting a highly accurate off-chip sense resistor; however, this increases the cost and bulk of the system. An on-chip resistor is the most cost-effective solution, but the above issues are aggregated and must be resolved.In this project, we will explore high-linearity current sensors with on-chip sensing resistor to achieve state-of-the-art linearity.The student will need to:1.Complete a comprehensive literature review on high-linearity current sensing.2.Propose a method to achieve area efficiency or high linearity.3.Make a concept-proof schematic design.4.If feasible, a tapeout will be supported.This work will build on an existing work that will soon be published. 5.Low-power Class-D audio amplifierClass-D audio amplifiers are widely used in many audio systems. Nowadays, in VR and smart glasses, low-power class-D audio amplifiers are highly demanded since these systems are battery-powered, and therefore, low power is highly critical.In this project, we will explore low-power Class D audio amplifiers for smart glasses. Not only the static idle power, but also the dynamic power consumption should be minimized.The student will need to:1.Complete a comprehensive literature review on low-power Class-D audio amplifiers.2.Propose innovative methods to minimize idle power consumption and dynamic power consumption.3.Make a concept-proof schematic design.4.If feasible, a tapeout will be supported.This work has several prior arts, e.g. H. Zhang et al., "A 121.7-dB DR and -109.0-dB THD+N Filterless Digital-Input Class-D Amplifier With an HV IDAC Using Tri-Level Unit Cells," in IEEE Journal of Solid-State Circuits, vol. 59, no. 12, pp. 4034-4044, Dec. 2024, doi: 10.1109/JSSC.2024.3432832.5.Current sensor for high-current power management systemsCurrent sensing is highly required in power management systems, such as motor drivers where the current can go up to 100A. Often, such current sensing is done with extra sensing components such as discrete shunt resistors, Hall sensors, and coils. These sensors increase the system cost and bulk. The power FET's own resistance Rdson can be used as the sensing element; however, it is highly temperature dependent and voltage dependent and thus often does not offer good accuracy.In this project, we will explore current sensing methods without using extra sensing elements and achieve 1% inaccuracy.The student will need to:1.Complete a comprehensive literature review on low-power Class-D audio amplifiers.2.Propose innovative methods to minimize idle power consumption and dynamic power consumption.3.Make a concept-proof schematic design.4.If feasible, a tapeout will be supported.This work has a prior art, including proven concepts and experimental results, which will be published soon.6.Self-calibrated precision amplifier Precision amplifiers are widely used in many applications such as industrial applications, medical applications, power management applications and etc. Precision amplifiers need to offer microvolts offset, low input current, high CMRR and PSRR. To achieve these, many precision amplifiers employ chopping and autozeroing, but at the cost of increased complexity, switching artifacts and chip area. Other precision amplifiers employ bipolar transistors to achieve low offset thanks to the intrinsic good matching, but they suffer from high input current. If the input current can be calibrated out at various temperatures, bipolar precision amplifiers have the potential to be an “all-around” precision amplifier!In this project, we will explore self-calibration techniques for bipolar precision amplifiers.The student will need to:1.Complete a comprehensive literature review on bipolar precision amplifiers.2.Propose innovative methods to self-calibrate the input current over a wide temperature range.3.Make a concept-proof schematic design.4.If feasible, a tapeout will be supported.This work has a reference prior art design: A CMOS Operational Amplifier Achieving ±5.8µV 3σ Offset and ±88nV/°C 3σ Offset Drift Using an On-Chip Heater-Based Self-Trimming Technique (accepted by ISSCC 2025)