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One example is the Philips NORBIT family of logic building blocks. The PMOS and I 2 L logic families were used for relatively short periods, mostly in special purpose custom large-scale integration circuits devices and are generally considered obsolete. For example, early digital clocks or electronic calculators may have used one or more PMOS ...
MOSFET (PMOS and NMOS) demonstrations Date Channel length Oxide thickness [1] MOSFET logic Researcher(s) Organization Ref; June 1960: 20,000 nm: 100 nm: PMOS: Mohamed M. Atalla, Dawon Kahng: Bell Telephone Laboratories [2] [3] NMOS: 10,000 nm: 100 nm: PMOS Mohamed M. Atalla, Dawon Kahng: Bell Telephone Laboratories [4] NMOS May 1965: 8,000 nm ...
The major drawback with NMOS (and most other logic families) is that a direct current must flow through a logic gate even when the output is in a steady state (low in the case of NMOS). This means static power dissipation, i.e. power drain even when the circuit is not switching, leading to high power consumption.
Alternatively, rather than static logic gates, dynamic logic such as four-phase logic was sometimes used in processes that did not have depletion-mode transistors available. For example, the 1971 Intel 4004 used enhancement-load silicon-gate PMOS logic , and the 1976 Zilog Z80 used depletion-load silicon-gate NMOS.
Similarly to early PMOS and NMOS CPU designs using enhancement mode MOSFETs as loads, depletion-load nMOS designs typically employed various types of dynamic logic (rather than just static gates) or pass transistors used as dynamic clocked latches. These techniques can enhance the area-economy considerably although the effect on the speed is ...
Designers predominantly used MOSFET transistors with pMOS logic in the early 1970s, switching to nMOS logic after the mid-1970s. nMOS had the advantage that it could run on a single voltage, typically +5V, which simplified the power supply requirements and allowed it to be easily interfaced with the wide variety of +5V transistor-transistor ...
As the electron mobility in the n-type channel of NMOS MOSFETs is about three times that of the hole mobility in the p-type channel of PMOS MOSFETS, NMOS logic allows for an increased switching speed. For this reason NMOS logic quickly began to replace PMOS logic. By the late 1970s, NMOS microprocessors had overtaken PMOS processors. [16]