|
Riposte Ivor Catt. 18june02 Displacement Current Drivel Found by Google http://www.physics.umd.edu/deptinfo/facilities/lecdem/k2-63.htm Clearly this guy lacks
confidence. “There is some discussion whether the actual pickup is due to
displacement current or simply some sort of general electromagnetic pickup,
that is obviously filling the area.” More honest than most. Give him B minus.
- Ivor Catt, 23may02 http://maxwell.byu.edu/~spencerr/websumm122/node72.html “Taking this as a hint, Maxwell made the
hypothesis that the vacuum was not really empty at all, but was instead
filled with atoms of a very fine and insensible material which he called the ether. When electric energy
was stored in space, Maxwell took this to mean that the atoms of the ether
became stretched, just like the atoms in paper or oil.” I have Maxwell’s Treatise. What page please?
Ivor Catt 23may02 Time-dependent
simulation
The time-dependent form of the drift-diffusion equations
can be used both for steady-state and transient calculations. Steady-state
analysis is accomplished by starting from an initial guess, and letting the
numerical system evolve until a stationary solution is reached, within set
tolerance limits. This approach is seldom used in practice, since now robust
steady-state simulators are widely available. It is nonetheless an appealing
technique for beginners since a relatively small effort is necessary for
simple applications and elementary discretization approaches. If an explicit
scheme is selected, no matrix solutions are necessary, but it is normally the
case that stability is possible only for extremely small timesteps. The simulation of transients requires the knowledge of
a physically meaningful initial condition, which can be obtained from a
steady-state calculation. The same time-dependent numerical approaches used
for steady-state simulation are suitable, but there must be more care for the
boundary conditions, because of the presence of displacement current during
transients. In a transient simulation to determine the steady-state, the
displacement current can be neglected because it goes to zero when a
stationary condition is reached. Therefore, it is sufficient to impose on the
contacts the appropriate potential values provided by the bias network. In a
true transient regime, however, the presence of displacement currents
manifests itself as a potential variation at the contacts, superimposed to
the bias, which depends on the external circuit in communication with the
contacts. Neglect of the displacement current in a transient is equivalent to
the application of bias voltages using ideal
voltage generators, with zero internal impedance. In such a situation, the
potential variations due to displacement current drop across a short circuit,
and are therefore cancelled. In this arrangement, one will observe the
shortest possible switching time attainable with the structure considered,
but in practice an external load and parasitics will be present, and the
switching times will be normally longer. A simulation neglecting displacement
current effects may be useful to assess the ultimate speed limits of a device
structure. Some very pretty looking pure drivel is at: http://webug.physics.uiuc.edu/courses/phys112/spring97/LECTURES/lect22/sld007.htm
|
|
|
|
|