Nand Chip works not good

Posted by 1291115416_user on May 17, 2022; 4:51pm
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/Nand-Chip-works-not-good-tp4036805.html

I tried three way to implement And with Nand,here is it

CHIP And {
    IN a, b;
    OUT out;

    PARTS:
    Nand(a = a,b= b,out= o1);
       
        //1-ok
        //Nand(a = a,b= b,out= o2);
        //Nand(a = o1,b= o2,out= out);
       
        //2- ok
        Nand(a= o1,b= o1,out= out);
       
        //3-NG
        //Not(in = o1,out = out);
}

I though the second and third should be the same, but actully not(Simulator Fail).
And I don't know why,