simulation, or /\/\/\/\/\------/\/\/\/\/\/-----

circuit simulation can be a very handy tool for working out circuit designs, debugging problems you are having on a board, doing what-if cases etc. choice of simulators is a combination of availability, user's taste capability and adaptability. the simulator i am favoring now is linear technology's switchercadIII ( http://www.linear.com/designtools/software/index.jsp#Spice ), windows freeware based on Berkeley SPICE 3F5 (i believe). for a long time i was using the text based spiceopus ( http://www.fe.uni-lj.si/spice/ ), put out by a university in slovenia. this is windows freeware too and it can be pretty dangerous, but is text based so there are no schematics to refer to which bugs some people out. the good thing is using a text netlist based simulator will force you to learn the spice syntax, which is done well and almost universally supported. the berkeley spice page is here: http://bwrc.eecs.berkeley.edu/Classes/icbook/SPICE/ with the full definition of the language and a bit of the history. the short version of it is that spice was developed in the 70s as a mesh conductance solver to simulate the early integrated circuits that were being developed, where hand calculation of the circuit parameters was pretty tough to do. since then the basic language has gone thru a couple of revs but is still pretty similar, sort of like old english, middle english, modern english. only now is the conductance matrix method of spice starting to age, because most of the very high frequency work being done now requires full wave 3d solvers, which simulate fields and waves directly, and don't rely on lumped circuit elements. anyway, spice has been around for a long time and is a reliable, accurate (for circuits anyway) and useful thing to get acquainted with. AND you can simulate tube circuits with it, because the language is made to support generic subcircuits that can describe any kind of electronic device, past or present. switchercad is really flexible because it is mostly based on editable text parameters, so if you have the time you can customize it a lot and make it do a lot of things it doesn't do out of the box. all of the stuff i post here will probably be in switchercad schematic files, i'm not sure if i am going to post spice netlists or not, depdending on how the file access works out. on a side note, there is also a free version of PSPICE out there, but i find it a lot harder to customize, add models, etc. it does have a pretty nice schematic editor and more simulation features though, but the model editor drives me totally crazy so i have put it aside for the simple text interface of switchercad. there are also a lot of other flavors of spice out there, so see what works for you, the cool thing about spice is they are all fundamentally pretty similar but have different 'extras' built on top of the basic spice syntax, so it usually isn't too hard to covert one flavor to another. YMMV tho...