Multiple-input NOR logic design using negative differential resistance circuits implemented by standard SiGe process

A multiple-input NOR logic gate using the negative differential resistance (NDR) circuit is demonstrated. The NDR circuit is composed of four resistors (R) and two SiGe-based heterojunction bipolar transistor (HBT), and it can show the NDR characteristics in the combined current–voltage curve by suitably designing the resistance. Compared to the resonant tunneling diode, the R–HBT–NDR circuit is much easier to be applied to some circuits which are combined with other Si-based or SiGe-based devices and circuits on the same chip. The fabrication is based on the standard 0.35 μm SiGe BiCMOS process.