A novel delta-sigma modulator using resonant-tunneling quantizers

A /spl Sigma//spl Delta/ modulator based on ultrahigh-speed compound semiconductor technology is proposed. Resonant tunneling diodes (RTDs) are employed for a multi-GHz quasi-differential quantizer. High electron mobility transistors, or HEMTs, with a unity-current-gain cutoff frequency of 150 GHz are also used to obtain integrators. Our transistor-level circuit simulation for a 2nd-order continuous-time /spl Sigma//spl Delta/ modulator exhibits clear noise-shaping characteristics at a sampling frequency of 4 GHz. This proves high potential of the present RTD-based circuit.