<p>Comparator is the main building block in an ADC architecture. Main purpose of the comparator is to compare a signal with a reference signal and produce an output depending on whether the input signal is greater or smaller than reference. Many architectures for comparators exist for various purposes. In this thesis, Latched comparator architecture is used for sigma delta modulator. This particular design has two main characteristics that are very important for sigma delta application. First characteristic is the cancellation of memory effect which increases the speed and reliability of the system and the second is, with this architecture, high sensitivity can be achieved.</p><p>The design and implementation of lathed comparator for sigma delta modulator is presented in this thesis work. Various non-linearities and performance parameters are discussed in detail. Practical implementation and circuit design issues are highlighted to achieve maximum sensitivity along with reasonable speed and accuracy.</p>

Comparator is the main building block in an ADC architecture. Main purpose of the comparator is to compare a signal with a reference signal and produce an output depending on whether the input signal is greater or smaller than reference. Many architectures for comparators exist for various purposes. In this thesis, Latched comparator architecture is used for sigma delta modulator. This particular design has two main characteristics that are very important for sigma delta application. First characteristic is the cancellation of memory effect which increases the speed and reliability of the system and the second is, with this architecture, high sensitivity can be achieved. The design and implementation of lathed comparator for sigma delta modulator is presented in this thesis work. Various non-linearities and performance parameters are discussed in detail. Practical implementation and circuit design issues are highlighted to achieve maximum sensitivity along with reasonable speed and accuracy.

<p>Analog-to-digital converters (ADC) targeted for use in medical implant devices serve an important role as the interface between analog signal and digital processing system. Usually, low power consumption is required for a long battery lifetime. In such application which requires low power consumption and moderate speed and resolution, one of the most prevalently used ADC architectures is the successive approximation register (SAR) ADC.This thesis presents a design of an ultra-low power 9-bit SAR ADC in 0.13μm CMOS technology. Based on a literature review of SAR ADC design, the proposed SAR ADC combines a capacitive DAC with S/H circuit, uses a binary-weighted capacitor array for the DAC and utilizes a dynamic latch comparator. Evaluation results show that at a supply voltage of 1.2V and an output rate of 1kS/s, the SAR ADC performs a total power consumption of 103nW and a signal-to-noise-and-distortion ratio of 54.4dB. Proper performance is achieved down to a supply voltage of 0.45V, with a power consumption of 16nW.</p>

Analog-to-digital converters (ADC) targeted for use in medical implant devices serve an important role as the interface between analog signal and digital processing system. Usually, low power consumption is required for a long battery lifetime. In such application which requires low power consumption and moderate speed and resolution, one of the most prevalently used ADC architectures is the successive approximation register (SAR) ADC.This thesis presents a design of an ultra-low power 9-bit SAR ADC in 0.13μm CMOS technology. Based on a literature review of SAR ADC design, the proposed SAR ADC combines a capacitive DAC with S/H circuit, uses a binary-weighted capacitor array for the DAC and utilizes a dynamic latch comparator. Evaluation results show that at a supply voltage of 1.2V and an output rate of 1kS/s, the SAR ADC performs a total power consumption of 103nW and a signal-to-noise-and-distortion ratio of 54.4dB. Proper performance is achieved down to a supply voltage of 0.45V, with a power consumption of 16nW.

The majority of signals, that need to be processed, are analog, which are continuous and can take an infinite number of values at any time instant. Precision of the analog signals are limited due to influence of distortion which leads to the use of digital signals for better performance and cost. Analog to Digital Converter (ADC), converts the continuous time signal to the discrete time signal. Most A/D converters are classified into two categories according to their sampling technique: nyquist rate ADC and oversampled ADC. The nyquist rate ADC operates at the sample frequency equal to twice the base-band frequency, whereas the oversampled ADC operates at the sample frequency greater than the nyquist frequency. The sigma delta ADC using the oversampling technique provides high resolution, low to medium speed, relaxed anti-aliasing requirements and various options for reconfiguration. On the contrary, resolution of the sigma delta ADC can be traded for high speed operation. Data sampling techniques plays a vital role in the sigma delta modulator and can be classified into discrete time sampling and continuous time sampling. Furthermore, the discrete time sampling technique can be implemented using the switched-capacitor (SC) integrator and the switched-current (SI) integrator circuits. The SC integrator technique provides high accuracy but occupies a larger area. Unlike the SC integrator, the SI integrator offers low input impedance and parasitic capacitance. This makes the SI integrator suitable for low supply voltage and high frequency applications. From a detailed literature study on the multi-bit sigma delta modulator, it is analyzed that, theneeds a highly linear digital to analogue converter (DAC) in its feedback path. The sigma delta modulators are very sensitive to linearity of the DAC which can degrade the performance without any attenuation. For this purpose T.C. Leslie and B. Singh proposed a Hybrid architecture using the multi-bit quantizer with a single bit DAC. The most significant bit is fed back to the DAC while the least significant bits are omitted. This omission requires a complex digital calibration to complete the analog to digital conversion process which is a small price to pay compared to the linearity requirements of the DAC. This project work describes the design of High-Speed Hybrid Current modeModulator with a single bit feedback DAC at the speed of 2.56GHz in a state-of-the-art 65 nm CMOS process. It comprises of both the analog and digital processing blocks, using T.C. Leslie and B. Singh architecture with the switched current integrator data sampling technique for low voltage, high speed operation. The whole system is verified mathematically in matlab and implemented using signal flow graphs and verilog a code. The analog blocks like switched current integrator, flash ADC and DAC are implemented in transistor level using a 65 nm CMOS technology and the functionality of each block is verified. Dynamic performance parameters such as SNR, SNDR and SFDR for different levels of abstraction matches the mathematical model performance characteristics.

This diploma thesis deals with design methods and optimization techniques of dynamic latched comparators. It compares latched and continuous comparators and describes their principle. Then it analyses three popular latched comparator structures with respect to offset, speed and kickback noise. It shows practical comparator design focused on offset precision.