A 581/781 MSPS 3-BIT CMOS FLASH ADC USING TIQ COMPARATOR IJECET © I A E M E

ABSTRACT Analog to digital converters (ADCs) is a mixed signal device that converts analog signals which are real world signals to digital signals (which are binary in nature) for processing the information.Since signal processing in digital domain has widely being studied, designing an analog-to-digital converter has become more challenging for the researchers. In the digital domain, low power and low voltage requirements are becoming more important issues as the channel length of MOSFET shrinks below 0.25 sub-micron values. In this paper, a novel flash analog-to-digital converter for low-power & high speed applications has been proposed by incorporating the threshold inverter quantization technique. The key idea of this technique is to generate 2 n -1 different sized threshold inverter quantization comparators for an n-bit converter due to which the fast data conversion speed improves the operating speed and the elimination of ladder resistors leads significant reduction in the power consumption. The use of two cascaded inverters as a voltage comparator is the reason for the technique's name (TIQ). To construct an n-bit flash TIQ based ADC, one must find 2 n -1 different inverters, each has different V m value, and one must arrange them in the order of their V m value. The gain boosters make sharper thresholds for comparator outputs and provide a full digital output voltage swing. The comparator outputs -the thermometer code -are converted to a binary code in two steps through the `01' generator and the encoder. The proposed 3-bit flash ADC using TIQ is designed using FAT tree encoder and simulated with the help of TANNER-EDA tool in 0.25 µm CMOS technology. This paper represents 3-bit flash ADC for supply voltage of 2.5Vand 3.3 V. Also transistor sizes are varied from 1.5µm to 12.1µm for different widths, for input frequency of 1 MHz and speed and power for different variation are estimated. The optimum values of Power and Speed are being chosen amongst the obtained values