LTSpice

Since LTSpice has been around, I have started to simulate circuits with it. Simulations are not only faster than experimental setups on breadboards, they cost nothing (except time), nothing breaks, you don't burn your fingers and you can measure in places that are not accessible or are very difficult to access in real circuits.

Later, I made my own models wherever necessary.

Here I would like to introduce some of them which I consider remarkable.