Nonthreshold logic ring oscillators implemented with GaAs/(GaAl)As heterojunction bipolar transistors

The first nonthreshold logic (NTL) ring oscillators implemented with GaAs/(GaAl)As heterojunction bipolar transistors (HBT's) are reported. Propagation delay times down to 52 ps per gate were achieved, using transistors with emitter dimensions of 1.2 µm × 5 µm. Numerical simulations of the circuits were also done, which agreed closely with the experimental results.