Electrical

Pull-Up vs Pull-Down Digital Inputs

Electrical Diagrams · made in Skemio

Circuit diagram contrasting a pull-up resistor circuit and a pull-down resistor circuit connected to pushbuttons on a 5V DC line.
Circuit diagram contrasting a pull-up resistor circuit and a pull-down resistor circuit connected to pushbuttons on a 5V DC line.
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What it shows

  • A pull-up resistor ties the input pin to VCC, making LOW the active state.
  • A pull-down resistor ties the pin to GND, making HIGH the active state.
  • Typical 10 kΩ values limit current to 0.5 mA while sinking ambient noise.

The takeaway

Pull resistors define a deterministic default voltage so high-impedance inputs never float randomly.

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