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This slows the 0 to 1 transition, resulting in a slower circuit. Depletion-load processes replace this transistor with a depletion-mode NMOS at a constant gate bias, with the gate tied directly to the source. This alternative type of transistor acts as a current source until the output approaches 1, then acts as a resistor.
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.
For enhancement-mode and depletion-mode MOSFET symbols (in columns two and five), the source terminal is the one connected to the triangle. Additionally, in this diagram, the gate is shown as an "L" shape, whose input leg is closer to S than D, also indicating which is which.
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 ...
In the depletion-load NMOS logic realization in the middle below, the switches are the transistors T2 and T3, and the transistor T1 fulfills the function of the pull-up resistor. In the CMOS realization on the right below, the switches are the n-type transistors T3 and T4, and the pull-up resistor is made up of the p-type transistors T1 and T2 ...
The depletion region has to be closed to enable current to flow. JFETs can have an n-type or p-type channel. In the n-type, if the voltage applied to the gate is negative with respect to the source, the current will be reduced (similarly in the p-type, if the voltage applied to the gate is positive with respect to the source).
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 ...