Design a bandgap reference current in tsmc 28nm

Abstract

An important part in the design of analog integrated circuits is to create reference voltages and currents with well-defined values. To accomplish this on-chip, so called bandgap reference circuits are commonly used. A typical application for reference voltages is in analog-to-digital conversion, where the input voltage is compared to several reference levels in order to determine the corresponding digital value. The emphasis in this thesis work lies on theoretical understanding of the performance limitations as well as the design of a bandgap reference circuit, BGR.

This thesis briefly presents the basic CMOS knowledge, some analog circuits and layout techniques for analog circuits. The project proposes the design of a current reference. A design procedure for the generation of a reference using a MOSFET-only circuit is proposed. The design consists of a simple current generation circuit with its transistors biased at their respective zero temperature coefficient (ZTC) points and the startup circuit help the main circuit operate correctly when power on.

The transistor-level circuit for the generation of a 60µA ± 30% current reference is designed according to the proposed design procedure and its functionality is verified by simulation. This circuit is implemented in a TSMN 28nm process. This 60µA current reference circuit achieves a temperature coefficient of 11.5nA/oC over the operating temperature range of -40oC to 125oC and with supply voltage 1.2V ± 5%. We also propose a layout design for the OPAMP block.