NMOSonly

NMOSonly refers to digital logic and integrated circuits designed using NMOS transistors exclusively, without PMOS or CMOS devices. In NMOSonly designs, a pull-up path provides a high output when the NMOS pull-down network is off, typically implemented with a resistor to the positive supply or with a depletion-mode NMOS transistor acting as a load.

Operation is based on a pull-down network of NMOS transistors. When the input combination enables a conduction path to ground, the output is driven low. When the pull-down is off, the load pulls the output toward the supply, yielding a high level. This produces static NMOS logic behavior, where gates implement logical functions through combinations of NMOS switches and a resistive or depletion-load pull-up.

Historically, NMOSonly logic was common in the 1970s and early 1980s, prior to CMOS dominance. It offers simple fabrication in NMOS processes and straightforward transistor-level design. However, it suffers from static power consumption whenever there is a conducting path to both supply and ground, has slower switching speeds due to the resistive or depletion-mode pull-up, and is less scalable than CMOS.

Today, NMOSonly designs are largely of historical and educational interest. They help illustrate transistor-level operation, threshold behavior, and the trade-offs among different logic families. Modern integrated circuits predominantly use CMOS, which provides much higher density and lower power for comparable functionality.