Analog circuit design has become such a niche that only a privileged few with access to expensive design suites and agreements with foundry to use PDK (process design kits) are able to acquire and hone their design skills. Usually, the work settings does not allow one to explore their own ideas that are off-track from the projects being executed.

Thanks to the renewed drive in open source tools development and foundries making their PDK available as open source, one can pursue their crazy ideas to execution and implementation.

The circuits that are public domain knowledge in the form of text books (shown below) or publications are used for learning and analyzing purpose.

Disclaimer: The purpose is to only understand and learn the functionality of various circuits. There is no performance guaranteed of the designs and no relation to any IPs what so ever.