4000 series cmos

logic IC family that runs from ~3–15 V, slower but friendly. each chip is a logic function (AND, OR, NOT, flip-flop, counter…).

starter parts

• 4011: quad NAND
• 4001: quad NOR
• 4040 / 4060: ripple/divider counters (4060 includes oscillator pins)
• 4017: decade counter (great for LED chasers)

rules

• decouple every chip (0.1 µF at VDD/GND).
• don’t float inputs: tie unused inputs high or low.
• limit fan-out; buffer LEDs with resistors or transistors.