74 series ttl

modern hobby builds usually use 74HCxx (CMOS) at 3.3–5 V. HCT has TTL-compatible input thresholds for mixing with 5 V TTL.

common picks

• 74HC00: quad NAND
• 74HC14: hex Schmitt inverter (debounce helper!)
• 74HC595: serial-in, parallel-out (LED expansion)
• 74HC165: parallel-in shift register (read many buttons)
• 74HC4051: 8-ch analog mux

notes

• HC: ~2–6 V supply. HCT: 5 V supply with TTL-like input thresholds (plays nice with LS/TTL outputs).
• decoupling: 0.1 µF per chip, right at VCC/GND pins.