what is a pull up resistor

A pull-up resistor is an electronic component used in circuit design to ensure that a signal line is in a high state (logic 1) when it is not being actively driven by an output device. It is typically used in combination with a switch or a digital input to prevent the input line from floating, which could cause erratic behavior in the circuit. The pull-up resistor is connected between the signal line and the voltage supply line, and its resistance value is chosen to provide a voltage level that is within the acceptable high range for the input device. This ensures that the signal line is at a known state when no active signal is present. Overall, a pull-up resistor helps to stabilize and improve the reliability of digital circuits by preventing unexpected signal fluctuations. It is commonly used in microcontroller-based systems, digital sensors, and other electronic devices.