What tool do you use for analog simulations and how well does it work ?
Hi Dan, Great question ! Our preferred analog simulation tool is LTSpice, we like it because it is easy to use, has a lot of capabilities and now that LT is part of Analog Devices we are starting to see a great selection of AD Opamps in the built-in library which saves a lot of time. Generally we find LTSpice to be very effective as a simulation engine, there are a few limitations like needing to manually enter step functions for families of simulations measurements such as Monte Carlo analysis or variations with temperature, and the usual making sure that simulations converge etc. but overall the results are pretty accurate. For comparison I recently did some noise simulations and compared with the theoretical results derived using an xl spreadsheet and modelling voltage/current noise, resistors etc and the results were very close. One thing we do notice is that the Analog Devices models tend to give more accurate results than some we've seen from other vendors ! Having said that the results are only as good as the models being used so for instance most op-amps use behavioral models rather than transistor level so the finer operating details may not always get caught. Models are often for "typical" devices so won't always reflect the worst case results. Finally the models tend to only be as good as the datasheet requirements so if the data sheet gives settling time to 0.1% good luck if you need 1ppm! The other thing to bear in mind is the lumped element models are for "ideal" components, so for use at RF and higher the parasitics need to be included. Overall given the right models LTSpice works well but I'd highly recommend prototyping to verify if the design requires anything exotic.