Been trying some other models, specifically diodes, on ngspice (see https://github.com/xorbit/sky130-power-blocks/blob/master/primitive-test/diode-test.spice). PNP as diode has a kind of high Vt close to 1V at low temp (which complicates making a low voltage bandgap). Simulation shows the Vt of some of the diodes to be much lower, less than 0.4V max. Is this real? I thought the Vt of any PN junction was physics and it wouldn't matter if it was a BE junction of a PNP or a well/diffusion diode. Anyway, I'm not sure how much to trust these diode simulations because there are all kinds of issues, lots of "no convergence" issues (a lot of the diode variants were commented out because of that) and bizarre behavior over temperature, with Vt completely disappearing, which I don't think a real diode does at any temperature.