When choosing the input voltage range,
the input common mode voltage range (VICR) must be taken in to account.
If operating temperature is above or below 25°C the VICR can range from
0V to VCC– 0.7V. This limits the input voltage range to as high as
VCC– 0.7V and as low as 0V. Operation outside of this range can yield
incorrect comparisons.
Below is a possible list of input
voltage situation and the outcomes:
- 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, the output is low and the output transistor is
sinking current