@User It is entirely possible I'm doing things wrong, it's been years since I've done anything like this and with different tools, so I'm trying to learn as I go. I'd love to see your control loop approach. It would probably be very helpful for doing temp sweep for ac analysis. I haven't been able to figure out how to do this, since the way I found to do this is by abusing a "dc analysis". Back in the day my simulator allowed .temp statement and that was that, but it seems ngspice doesn't do that.