When choosing the input voltage range, the input common-mode voltage range (V_ICR) must be taken in to account. If temperature operation is above or below 25°C the V_ICR can range from 0 V to V_CC– 2 V. This limits the input voltage range to as high as V_CC– 2 V and as low as 0 V. Operation outside of this range can yield incorrect comparisons.

The following list describes the outcomes of some input voltage situations.

• When both IN– and IN+ are both within the common-mode range:
  • If IN– is higher than IN+ and the offset voltage, the output is low and the output transistor is sinking current
  • If IN– is lower than IN+ and the offset voltage, the output is high impedance and the output transistor is not conducting
• When IN– is higher than common mode and IN+ is within common mode, the output is low and the output transistor is sinking current
• When IN+ is higher than common mode and IN– is within common mode, the output is high impedance and the output transistor is not conducting
• When IN– and IN+ are both higher than common mode, see Section 2 of Application Design Guidelines for LM339, LM393, TL331 Family Comparators Including the New B-versions