Journal of VLSI Design Tools and Technology Volume 3, Issue 1, ISSN: 2249- 474X __________________________________________________________________________________________ JoVDTT(2013) 14-19 © STM Journals 2013. All Rights Reserved Page 14 A New Sub-1 Volt Reference for Low Voltage Application Based on MOSFET’s Threshold Voltage Extractor Anil Kumar Saini 1 *, Megha Agarwal 2 1 CSIR-Central Electronics Engineering Research Institute, Pilani, India 2 Thapar University, Patiala, India Abstract A CMOS voltage reference circuit featuring MOS transistors threshold voltage extractor has been developed. The circuit implemented using 0.35μm CMOS AMS process generates a reference of 574 mV for a power supply of 3.3V with 726μW power consumption. The circuit presents a variation of 43 ppm/ºC for the –10 to – 110ºC temperature, and 18.6 dB PSRR at 1 KHz. A vital analytical approach is presented to provide a universal design guideline. Keywords: threshold voltage extractor, low-voltage, process variation, CMOS bandgap voltage reference *Author for Correspondence E-mail: anilsaini.ceeri@gmail.com INTRODUCTION Voltage reference is the key component in the design of many analog and mixed signals application including phase locked loop (PLL), analog-to-digital (A/D) convertor and digital-to-analog (D/A) convertor. A voltage reference must be inherently well-defined and insensitive to temperature, power supply and load variations. The resolution of an A/D or D/A converter is limited by the precision of its reference voltage over operating temperature ranges [1]. For this purpose, bandgap voltage references (BGR) are commonly used which provide stable and accurate reference voltage. These can be implemented in CMOS and bipolar technology. The proportional-to- absolute-temperature (PTAT) term is realized by amplifying the voltage difference of two forward-biased diodes (i.e., base-emitter junctions) then this is used to compensate the complement-to-absolute-temperature (CTAT) term which is realized by the forward voltage of a p-n junction diode or the base-emitter voltage of bipolar transistor [2]. Since, power supply plays an important role in circuit’s power consumption, for battery operated portable application, low voltage low power analog circuits are very important. The output voltage of classical bandgap reference circuit is 1.2 V. This fixed output voltage limits its use in low voltage application. A DTMOS (dynamic threshold MOSFET) bandgap voltage reference circuit has been developed for low power application but it is not compatible with CMOS technology [3]. This paper presents a novel voltage reference based on Vt extractors for low voltage application which provides temperature independent voltage reference over wide range of temperature variation. BASIC CONCEPTS T heory Review There are two ways to generate reference voltage independent of temperature variation.  By summing two voltage which has temperature coefficient of opposite sign such as bandgap reference [2]. V REF = V BE + k V t (1) Where V BE is generated a voltage from pn- junction diode having negative temperature coefficient. Also, generated is a thermal voltage V t , which has positive temperature coefficient.  By subtracting two voltages that vary in the same direction with temperature, authors choose k 1 and k 2 so as to achieve [4]: V REF = k 1 V 1 – k 2 V 2 (2) In both cases, suitable multiplication constant is used, which resulting voltage is independent of temperature. The bandgap voltage reference is bipolar in nature and when the supply