Implementation of High Speed Flash ADC Using Multiplexer with Reduced Number of Preamplifier and Comparator Count

A high speed Flash analog-to-digital converter (ADC) using multiplexer with reduced number of preamplifiers and comparators is introduced. A conventional N-bit flash ADC requires 2N-1 preamplifiers and comparators while The high speed flash ADC only needs 2 (N-3)) +2 preamplifiers and 2 (N-2) +1 comparators. For a 6-bit resolution, the high speed flash ADC requires a reduce number of preamplifiers and comparator, compare with those of the conventional flash ADC. The high speed flash 6-bit ADC consists of a reference ladder network, track and hold circuit, 10 preamplifiers, 17 comparators, a (2x1) -MUX, 8 (4x1) -MUXs and logic gates for encoder and registers. The high speed flash ADC is simulated with tanner suit 180nm CMOS process with 1-V supply voltage and consumes 0.378mW. At 50 MS/s, high speed flash ADC has the effective number of bits of 5.97-bit and the figure of merit of 0.12 pJ/conversion-step, signal to noise distortion ratio is 37.74 db and SFDR is 46.7 db.