What is the voltage of 8051 microcontroller?

Answer 1

This question is literally impossible to answer without knowing a specific part number (and manufacturer which is usually easy to determine because it is based off the part number). The 8051 was first used in the IBM type computer as the keyboard controller to send key presses to the CPU. It has since become an architecture that appears in a number of other places. There are several manufacturers that produce low cost and low power microcontrollers based upon the 8051 with other peripherals included in the same package. Because there are numerous 8051 controllers, there is no one standard for connecting them to power for each may design their controller to meet their own design guidelines.

Older 8051 microcontrollers usually require a 5 V power supply.

Newer 8051 microcontrollers are more likely to require a 3.3 V power supply.

The only way to tell is to read the part number off the chip and look up the manufacturer's data sheets for that part number.

Fortunately, most data sheets are online these days.