An ultrahigh-speed full adder using resonant-tunneling logic gates

An ultrahigh-speed full adder using resonant-tunneling diodes (RTDs) has been investigated by circuit simulation. The adder uses NOR logic gates, each of which consists of four RTDs (called 4RTD logic gate), with a four-phase pipelined scheme. Circuit simulation has been carried out by assuming an InP-based RTD device model, the peak current density and the peak-to-valley ratio of which are 5.0 times 10⁵ A/cm² and 10, respectively. The simulation shows that the full adder operates at a clock frequency as high as 50 GHz.