open-source-silicon.dev

Hello, I'm watching the video on YouTube about the design of an operational amplifier (<https://www.youtube.com/watch?v=XvBpqKwzrFY>). Is it really okay to connect all guard rings of a given transistor type (PMOS or NMOS) with Local Interconnect layer? I know that the routing with Local Interconnect is not recommended.

IIRC in that video they use really like "fills" (i.e. very wide) so the resistance isn't that bad. Guard ring is also just biasing so there isn't that much current that should go through there either.  Also depends the size of the transistor if the resistance is acceptable or not.

Ok, but the connection with metal 1 is also good, correct? In this case, it is necessary to put metal 1 on at least one side of the guard rings.

Sure, if you have the space to put `met1` by all mean. I try to overlay `met1` where I can and just make "holes" in the `met1` to get signals in/out.

There isn't "one answer", it depends on many factors and what you can live with.  If this is some sensitive circuit, you might want better connection for the guard ring.  If it just some random transistor ... maybe you can live without any guard ring at all ...