If your simulating tool is that stupid that it can't simulate a -174 dBm/Hz insertion into each stage why use it ??
I am fully aware that any garden variety simulation package is not capable of handling the feedback situation correctly.
I just asked, how multiple in series non-feedback stages would behave.
Sure you can do all kinds of simulations, but do these have anything to do with the real physical world (as in the climate change debate) ?
SPICE? Perhaps not but there were other circuit simulators that did run on computers without IEEE floats. Of course, there are other uses for floats, too. ;-)
The transient and ac response in spice handles 100 of filters no problem, you just can't feed it with a resistor to generate time based noise. If you want time based noise, you would have to set up a PWL (piece wise linear source) to model random noise. LTSpice will let you feed in a wav file, so it that is loaded with Lady Ga Ga, it should be a reasonable approximation to random noise. Why you would think Lady Ga Ga would be useful for analog design is a certainly mystery though.
If your car can't go 200 mph, why use it?
I have no idea what you are saying here.
Spice does AC and non-linear Transient analyses in enough detail to reliably design oscillators in the virtual world, so as such it handles "the feedback situation" fine.
However, to analyse phase noise, you need a steady state simulator i.e. PSS and PSS Noise, as available in packages such as Cadence Spectre R.F. This also costs lot of money. NGSpice has a developmental Periodic Steady State option, but there are no cheap useable phase noise analysis programs in the known universe.
Its not really a useful question. Oscillator design manages perfectly well without modelling start-up under noise conditions.
Yes. Spice simulations for analog ASIC design and development are, essentially, nuts on, and indispensible. Billions and billions of real world chips of 10,000s of different types, with 10,000s of transistors per asic, have been designed purely in the virtual world, in simulation. Period.
Climate debate is several orders of magnitude different. It requires the solution of huge partial differential equation systems, not ordinary differential equations. It also needs data. One sensor to measure temperature, pressure, humidity etc every cubic mile is also a huge number sensors. A wasp farting in china could cause a hurricane in Iceland. There are just too many unknowns in climate simulations. ASICs are pretty well defined.
Kevin Aylward B.Sc.
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The "wasp farting in China" is better known as the "butterfly in Brazil" an d is a problem with weather simulations, rather than climate simulations.
The climate is essentially a mechanism for transporting heat from the equat or to the poles. The weather - which does a lot of the work - is chaotic, b ut its fluctuations are constrained by thermodynamics.
The biggest unknown in the picture is that a lot of heat is shifted by ocea n currents which do meander around a bit over periods of years - decades wi th the Atlantic Multidecadal Oscillation. The Argo buoys are collecting dat a on the ocean currents - both the surface currents and the deep return cur rents - but there are so far only about 3600 of them. The program started a round 2000, and the number of papers being published per year on the result s crept up to about 120 in 2009, then leapt to about 220 in 2010, creeping on up to about 280 in 2013.
Ask a politician, especially the ones current in power in the US. The word "trillions" leaves them completely unfazed, they don't care. This nonsense actually started already with the Romans and nothing was learned from that. So why shouldn't the International Brotherhood of Oscillators claim the same right?
:-)
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