I'm currently trying to create a 4 bit ALU using the CD4011BE quad 2-input CMOS NAND gate ICs. However, I'm having some trouble when creating the full adders. Sometimes, when the IC outputs logic low, I'm getting 2.5V, which causes the next NAND gate to also output something like 2.5V. This carries down to the sum, which is 2.5V when supposed to be under 0.5V. I've read that ICs need decoupling capacitors, but I'm not sure if that would cause this problem
I'm testing this on a Breadboard, and running 5V rails.
EDIT: I've tried testing the voltage of each pin. Strangely, the ground pin had 1.5V while only being connected to ground. I tried replugging everything in, and it worked perfectly now.