Pullupvastuksia

Pullupvastuksia is a Finnish term that translates to "pull-up resistances" or "pull-up resistors" in English. It refers to a type of electrical resistor used in digital electronics. A pull-up resistor is connected between a signal line and a positive voltage supply (VCC or VDD). Its primary function is to ensure that the signal line has a defined, high voltage level when no other device is actively driving the line to a low state.

Without a pull-up resistor, a signal line might be left floating or in an indeterminate state when it's not actively driven. This can lead to unpredictable behavior in digital circuits, as the input of a logic gate might interpret stray electrical noise as a valid signal. By pulling the line up to the positive voltage, the pull-up resistor establishes a default high logic state.

Pull-up resistors are commonly used with open-collector or open-drain outputs, which can only actively pull a signal line low. When these outputs are not active, the pull-up resistor pulls the line high. They are also frequently used with buttons and switches to define the state of a digital input when the button is not pressed. In such configurations, pressing the button connects the signal line to ground (low voltage), and releasing it allows the pull-up resistor to pull the line high. The value of a pull-up resistor is typically chosen to be high enough to minimize current consumption but low enough to ensure a strong enough pull-up signal.