Flash Analog-to-Digital Converter Using Resonant-Tunneling Multiple-Valued Circuits

We have proposed a flash analog-to-digital converter (ADC) that uses resonant-tunneling complex gates not only as ternary quantizers but also as ternary-to-binary encoder circuits. The ternary quantizers, consisting of monostable-to-multistable transition logic (MML) circuits, convert the analog input signal into the ternary thermometer code. This code is then converted into the binary Gray-code output by a multiple-valued, multiple-input monostable-to-bistable transition logic element (M2-MOBILE). By assuming InP-based resonant-tunneling diodes and heterojunction field-effect transistors, we have carried out SPICE simulation that demonstrates ultrahigh-speed ADC operation at a clock frequency of 5 GHz. Compact circuit conjiguration, which is due to the combination of MML and M2-MOBILE, reduces the device count and power dissipation by a factor of two compared with previous RTD-based ADCs.