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The inclusion of depletion-mode NMOS transistors in the manufacturing process demanded additional manufacturing steps compared to the simpler enhancement-load circuits; this is because depletion-load devices are formed by increasing the amount of dopant in the load transistors channel region, in order to adjust their threshold voltage.
Such devices are used as load "resistors" in logic circuits (in depletion-load NMOS logic, for example). For N-type depletion-load devices, the threshold voltage might be about −3 V, so it could be turned off by pulling the gate 3 V negative (the drain, by comparison, is more positive than the source in NMOS).
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.
In depletion mode transistors, voltage ... The MOSFET is by far the most common transistor in digital circuits, ... CMOS logic displaced NMOS logic in the mid-1980s ...
A logic family of monolithic digital integrated circuit devices is a group of electronic logic gates constructed using one of several different designs, usually with compatible logic levels and power supply characteristics within a family. Many logic families were produced as individual components, each containing one or a few related basic ...
For the n-channel depletion MOS transistor, a sufficient negative V GS will deplete (hence its name) the conductive channel of its free electrons switching the transistor “OFF”. Likewise for a p-channel "depletion-mode" MOS transistor a sufficient positive gate-source voltage will deplete the channel of its free holes, turning it “OFF”.
This process was aided by the recent introduction of depletion mode NMOS logic, which greatly simplified the conceptual model of the active elements. [6] The mid-1970s were a period of rapid change as new processes were being introduced at different companies at a rapid pace. Each new process led to a set of design rules that often ran to 40 pages.
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 ...