Name:

          Rida Iftikhar

Project:

          Continuous time Delta Sigma

         modulator for low bandwidth

          biosensors applications

Discipline:

          Electronics

Institution:

          Quaid i Azam University, Islamabad, Pakistan

Submitted To:

          SSCS “PICO” Open-Source Chipathon

Contact: 

          ridaiftikhar@ele.qau.edu.pk

Dated:     

1^st May 2022

Executive Summary:

Delta sigma modulators have got a good fame for their use for Data Conversion applications. High resolution achievement due to oversampling, noise shaping and less sensitivity to circuitry nonidealities makes them most preferable over other type e.g. Nyquist rate converters. Delta sigma modulators provide an excellent means of trading precision for speed.

Following are the main components of a typical Delta sigma modulator as also shown in Fig. 1.

• Integrator (continuous or discrete time loop filter)
• Quantizer (typically two levels)
  • A/D which is a comparator for two levels
  • D/A which is a switch for two level

Fig: 1. The block diagram of a typical Delta sigma modulator.

Project Description:

There is an increased demand for portable devices as biological signal monitors. These devices are based on microelectronics in order to improve the Biosensing and are combination of transducers and biological sensing element.  Biosensors are of several types which are mainly classified as Disease detection, immunosensors and enzymatic biosensors etc. A low voltage sensing capability is another attraction for such devices.

In this project, a fully differential, continuous time delta sigma modulator with Cascade of integrators in feedback (CIFB) topology shall be developed for application as a biosensor, that can operate at voltage of less than 1V power supply.

The design of architecture composed of two different types of power efficient invertor-based Amplifiers, with single bit non Return-to-Zero Digital to Analog convertor. This low voltage invertor-based CT_SDM for low bandwidth consumes power in micro range.

Schematic:  Below we have circuitry diagram of a 3^rd order Delta sigma modulator with CIFB topology.