Two types of mos device PMOS: when g is 0, Switch on when g is i switch off: G-忙PMOs NMOS: when g is 1. switch on when g is 0. Switch off G-C NMOSPMOS: when G is 0, Switch on; when G is 1, Switch off; NMOS: when G is 1, Switch on; when G is 0, Switch off; Two types of MOS device