IMPLEMENTATION OF BANDGAP REFERENCE CIRCUITS

M. LINGADHAR REDDY2221213122

M.Tech-VLSI Design(2013-2015)

Under the guidance of Mr. G.SHIVA KUMAR

Assistant Professor,GITAM University,

Hyderabad.

CONTENTS

Introduction

Tool & technology

Approaches

Basic operation

Methodology

2 stage opamp

Implemented opamp

Simulation results

Here, we will learn how to produce a reference voltage

for given supply voltage. The band gap reference is an

electronic circuit to provide an accurate and stable voltage that

is very insensitive to the change in supply voltage and

temperature and also process parameters.

INTRODUCTION

Tool used - CADENCE VIRTUOSO

Technology – 90nm CMOS technology

TOOL & TECHNOLOGY

WHAT IS BGR AND WHY ??

In the design of analog integrated circuits its

important to create reference voltages and currents with

well defined values (constant). Especially in analog to

digital conversion, where the input voltage is compared to

several reference levels in order to determine the

corresponding digital value, a best application is this

bandgap reference voltages .

APPROACHES

Zener diode reference method

Enhancement and depletion reference method

Bandgap reference method

BASIC OPERATION

HOW BGR WORKS ?

Target: A fixed dc reference voltage that does not change with temperature.

kT/q has a positive temperature coefficient - PTAT proportional to absolute temperature

VBE of a BJT decreases with temperature - negative temperature coefficient

combine both to yield an approximatelyzero TC voltage reference

BASIC2 STAGE CMOS OPAMP

WHY OPAMP IN BGR ?

The first and probably the most important requirement is the DC

open-loop gain.

The bandwidth in which the application that uses VREF is operating

The noise from supply lines are strongly depend on the amplifier

design, consequently it is important to choose the best op-amp

architecture when the noise coming from the supply is a problem

IMPLEMENTED OPAMP

OPAMP RESULTS

Gain = 70 dB

Phase margin = 56

UGB= 60 MHz

IMPLEMENTED BGR

BGR results

Temperature vs. reference voltage

Noise analysis

Supply voltage vs. reference voltage

CONCLUSION

Here the detail study of operational amplifier design was studied and

implemented according to our requirement. Later different types of bandgap

reference methods discussed and finally bandgap voltage references

implemented as it is independent of temperature, power supply and noise.

Future work:

The present implemented circuit has some drawback (less variation)

with process parameters and would certainly need to have a constant

reference implementation.

thank you