There is some background work that needs to be done before diving in and designing circuits.
The first thing to do is decide on what software to use. Typically companies use very expensive CAD tools for layout, circuit simulation, and verification of integrated circuits. In addition to the CAD tools, one needs access to the PDK (Physical Design Kit) for the particular integrated circuit process that you want to design on. The PDK includes all of the specific information that you need to design in a particular process. This includes: Design Rule Checking (DRC), LVS (Layout vs. Schematic), PCELLS (parameterized drawings of each device in the process), and models for simulation.
I probably won’t be doing any layout or fabrication on this blog since the entire process is quite expensive, even using services like MOSIS. That said, there is still a need for circuit simulation software and models for a handful of devices.
Models for AMI’s 0.5um CMOS process is available on bakers website. The SPICE model file only includes NMOS and PMOS devices. Of course models are needed for diodes, BJTs, and resistors, but this is a good start.
For circuit simulation software, there a number of free circuit simulators. I’m going to be using Ngspice which is an open-source simulator based on an updated version of Berkley’s original SPICE simulator. There is no official GUI for this simulator, so the easiest way to use it is to write the netlist files by hand. This is exactly what I’ve decided to do. I’m not sure what to use to makes schematics, for now, maybe just paper, pencil and my cell-phone camera. LTSpice is another great free (but not open-source) circuit simulator that I may utilize from time to time.