The speed and power consumption of flash analog to digital converter (ADC) is governed by design of thermometer to binary (T2B) encoders used in it. In this study, ROM, Wallace tree, Fat tree and multiplexer (MUX) based encoders are compared for their performance. Power delay product analysis and bubble error analysis results suggest that the MUX based encoder may be preferred for use in flash ADCs. An improved new MUX based encoder is proposed which utilizes small 2:1 MUXs arranged in a more regular structure for the improvement in speed and power. The design of improved 15 to 4-bit MUX based encoder shows 19.1% and 14.2% improvement in speed and power respectively over conventional MUX based encoder.
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