What are some common logic voltages?

Common digital supply/logic voltages have trended downward over time to save power and suit smaller process nodes. Typical values include:

• 5 V — classic TTL and older CMOS.
• 3.3 V — very common for modern MCUs, FPGAs I/O, and interfaces.
• 2.5 V
• 1.8 V
• 1.5 V / 1.2 V — and even lower (e.g., ~0.9–1.0 V) for processor/FPGA core rails.

Many devices have separate I/O and core supplies, and mixed-voltage systems often require level shifters or level-tolerant I/O to interface safely between domains.