Application of resonant-tunneling quaternary quantizer to ultrahigh-speed A/D converter

An analog-to-quaternary quantizer using resonant-tunneling (RT) devices is applied to an ultrahigh-speed analog-to-digital (A/D) converter. First, transient analysis results for the quaternary quantizer, which consists of six RT diodes and one HEMT, are presented. A 4-bit A/D converter employing this quantizer with multiple-valued logic encoding circuits is then described. The number of transistors is one-fifth of that required for conventional A/D converters. SPICE simulation reveals that the present A/D converter can be operated at sampling rates as high as 4 GS/s.