Confused about voltage at electron level

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Discussion Overview

The discussion revolves around understanding voltage at the electron level, particularly in the context of NMOS transistors and the behavior of electric fields in transmission lines. Participants explore the nature of voltage differences, the movement of charge, and the implications of electric fields in semiconductor devices.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that voltage has no meaning without a reference point and emphasizes the importance of voltage difference between points A and B.
  • Another participant describes the behavior of an NMOS transistor, mentioning the high impedance of the gate and the minimal current draw, which includes charging the gate capacitance and leakage current.
  • A question is posed about how the electric field propagates down a transmission line and whether voltage is proportional to the number of electrons.
  • One participant suggests that the gate of the NMOS transistor is doped to create a deficiency of electrons, allowing for electron movement between doped silicon layers.
  • There is a discussion about visualizing voltage levels on a trace, questioning whether a 3V line would have more electrons compared to a 5V line and expressing uncertainty about electron behavior in relation to their fields.
  • Another participant argues that it is not about having more electrons but rather the same electrons moving faster at different voltage levels.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the nature of voltage and electric fields, with no consensus reached on the specifics of how these concepts manifest at the electron level. Disagreements exist about the interpretation of voltage in relation to electron density and movement.

Contextual Notes

Participants have not delved deeply into the physics of electromagnetics, which may limit the discussion's depth regarding the behavior of electric fields and charge movement.

NoName707
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Ok, so I've been struggling with understanding voltage down to the electron level. I know a voltage by itself has no meaning. We want a voltage difference. i.e. voltage diff between point A and B and that ground really has no meaning except as a reference. and i know that current is the movement of charge and that voltage is the electric field. my question is as follows.

Say I have an NMOS transistor which i am turning on and off with a switch. being a high impedance input (gate) there will be very minimal current draw.perhaps current to charge the line+gate capacitance and leakage current. If this is considered a transmission line, we will see the voltage move down the trace as a wave perhaps taking 1ns to move 6 inches. what exactly is happening here? How is the electric field moving down? is the voltage proportional to the number of electrons? i know the voltage is a force, but the force has to come from something.

Thanks!
 
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let me first state that i don't know what I'm talking about :biggrin: but i'll try. from what i know it is the fact that the gate had been doped so that it's missing electrons, and all that's happening a middle layer of doped silicon that has been depleted of an electron in the outer layer of atoms in a boron-silicon bond gets back it's electrons allowing an two/three layers of doped phosphorus-silicon bond with extra electrons to pass (jump to the next outer shell of the next closest conductor). the reason for the high capacitance and resistance is because of the area of the gate, the small breakdown voltage of the gate is due to how thin it is. the current from drain to source should be proportional to the voltage at the gate.
 
light_bulb, thanks! i was actually talking more about the electric field moving down the trace as a wave. If i were to visually depict the voltage on a trace what would a 3V line look in comparision to a 5V line? just more electrons? I didn't think electrons could just bunch up next to each other because their fields would tend to push them away from each other.

I know there are will be more "field lines" but what causes these extra "field lines"
 
NoName707 said:
If i were to visually depict the voltage on a trace what would a 3V line look in comparision to a 5V line? just more electrons? I didn't think electrons could just bunch up next to each other because their fields would tend to push them away from each other.

I know there are will be more "field lines" but what causes these extra "field lines"

not more electrons, the same electrons moving faster as far as the other questions i haven't jumped into the physics type stuff like electromagnetics yet.
 

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