CMOS requires very tight tolerances for the PMOS + NMOS transistors to cancel each other out exactly. Otherwise it doesn't work at all. In particular, you need

CMOS requires very tight tolerances for the PMOS + NMOS transistors to cancel each other out exactly. Otherwise it doesn't work at all. In particular, you need to ensure that the PMOS and NMOS turn on at the same voltage, otherwise you risk just shorting Vcc to Vss (aka: Power to Ground). NMOS was common in the 1970s before CMOS on silicon was figured out. I'm surprised to hear that this circuit is old-school NMOS, but I probably shouldn't be, as the CMOS step took a lot of research and effort back then.... If we're still at NMOS stage of production on this process, then its probably more relevant to think of analog-based designs. CMOS seems necessary if anyone is to achieve low-power modern-like designs. NMOS was still core to a lot of older chips though, so digital logic still can work on that. But the power consumption will be necessarily huge in comparison to CMOS.