LM139D datasheet by Texas Instruments

LM139D 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 the supply voltage (Vcc) + 0.3V. Exceeding this voltage can cause damage to the device.
• How do I ensure that the comparator output is not oscillating?
  To prevent oscillation, ensure that the input signals are properly filtered and decoupled, and that the output is properly loaded. Additionally, adding a small capacitor (e.g. 10nF) between the output and ground can help to reduce oscillations.
• What is the minimum input voltage required for the comparator to function correctly?
  The minimum input voltage required for the comparator to function correctly is typically around 1.5V to 2V, depending on the specific application and noise conditions.
• Can I use the LM139D as a zero-crossing detector?
  Yes, the LM139D can be used as a zero-crossing detector. However, it's essential to ensure that the input signals are properly conditioned and filtered to prevent false triggering.
• How do I choose the correct pull-up resistor value for the output?
  The pull-up resistor value depends on the specific application and load requirements. A general rule of thumb is to choose a value between 1kΩ to 10kΩ, but this may need to be adjusted based on the specific requirements of the system.