If anyone is thinking of having a go with SPICE circuit simulation, now may be a good time ...
... why? Because
Dave is doing some nice YouTube tutorials!

You can download LTspice IV
here.
There is a load of stuff about LTspice on the internet (and about SPICE in general, of course), but first off you might find the
LTwiki useful.
Hours of fun!
Let's get some circuits modeled, then posted here on the forum for all to admire!
