LM311DT datasheet by STMicroelectronics

LM311DT Frequently Asked Questions (FAQs)

• What is the maximum voltage that can be applied to the input pins?
  The maximum voltage that can be applied to the input pins is ±30V, but it's recommended to keep it within the supply voltage range (VCC - 2V to VCC + 0.3V) to ensure proper operation.
• How do I ensure the comparator output is not oscillating?
  To prevent oscillation, add a small capacitor (e.g., 10nF) between the output and ground, and a pull-up resistor (e.g., 1kΩ) between the output and VCC. This helps to filter out noise and ensure a stable output.
• What is the minimum input voltage difference required for a valid output?
  The LM311DT can detect input voltage differences as small as 1mV, but for reliable operation, it's recommended to have at least 5mV to 10mV of input voltage difference.
• Can I use the LM311DT as a zero-crossing detector?
  Yes, the LM311DT can be used as a zero-crossing detector. However, it's essential to ensure the input signal is properly biased and the comparator is configured for a valid output. A small hysteresis (e.g., 1mV) can help prevent oscillations.
• How do I choose the right pull-up resistor value for the output?
  The pull-up resistor value depends on the load current and the desired output voltage. A general rule of thumb is to choose a value between 1kΩ and 10kΩ. For example, if the load current is 1mA, a 1kΩ pull-up resistor would be suitable.