SLOA277B january   2019  – july 2023 LM124 , LM124-N , LM124A , LM158 , LM158-N , LM158A , LM224 , LM224-N , LM224A , LM258 , LM258-N , LM258A , LM2902 , LM2902-N , LM2902-Q1 , LM2902K , LM2902KAV , LM2904 , LM2904-N , LM2904-Q1 , LM2904B , LM2904B-Q1 , LM2904BA , LM321 , LM324 , LM324-N , LM324A , LM358 , LM358-N , LM358A , LM358B , LM358BA , TS321 , TS321-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Devices Covered in Application Note
    1. 1.1 Common Schematic
    2. 1.2 Base Part Numbers
    3. 1.3 Input Voltage Offset Grades
    4. 1.4 Maximum Supply Voltage
    5. 1.5 High Reliability Options
    6. 1.6 HBM ESD Grade
    7. 1.7 LM358B, LM358BA, LM2904B, LM2904BA, LM324B, LM2902B
  5. 2Input Stage Considerations
    1. 2.1 Input Stage Schematic
    2. 2.2 Input Common Mode Range
    3. 2.3 Input Impedance
    4. 2.4 Phase Reversal
  6. 3Output Stage Considerations
    1. 3.1 Output Stage Schematic, VOL and IOL
    2. 3.2 IOL and Common Mode Voltage
    3. 3.3 Output Stage Schematic, VOH and IOH
    4. 3.4 Short Circuit Sourcing Current
    5. 3.5 Output Voltage Limitations
  7. 4AC Performance
    1. 4.1 Slew Rate and Bandwidth
    2. 4.2 Slew Rate Variability
    3. 4.3 Output Crossover Time Delay
    4. 4.4 First Crossover Example
    5. 4.5 Second Crossover Example
  8. 5Low VCC Guidance
    1. 5.1 Low VCC Input Range Supporting –40°C
    2. 5.2 Low VCC Output Range Supporting –40°C
    3. 5.3 Low VCC Audio Amplifier Example
  9. 6Comparator Usage
    1. 6.1 Op Amp Limitations
    2. 6.2 Input and Output Voltage Ranges
    3. 6.3 Overload Recovery
    4. 6.4 Slew Rate
  10. 7Unused Amp Connections and Inputs Connected Directly to Ground
    1. 7.1 Do Not Connect Inputs Directly to Ground
    2. 7.2 Unused Amplifier Connections
  11. 8Conclusion
  12. 9Revision History

2.4 Phase Reversal

Under certain conditions, the polarity of the output voltage can become inverted. This scenario, called "phase reversal," occurs when the input of the amplifier violates the common-mode voltage range. Figure 2-4 region ‘A’ shows output phase reversal from an invalid input voltage. A negative input voltage, relative to a grounded V– pin, may come from unexpected sources, such as switching noise or ground bounce in DC to DC converters. Negative input voltages can also arise when rapid fall times and large capacitors combine to temporarily set a negative voltage at the input. An input voltage of less than –0.3 V can cause parasitic diode conduction that results in the output assuming the minimum VOL or maximum VOH level. Operation in this region is not defined in the data sheet as it violates the absolute maximum specification for input voltage. The input current turns on internal parasitic NPN transistors that steal current from other internal nodes causing output phase reversal.

Do not try to determine phase reversal performance empirically as different units may have different performance. Negative inputs must be avoided, assuming a single supply configuration, unless the application can accept either the VOL or VOH level during the duration of the negative input. In cases where a negative input voltage cannot be avoided, use a resistor in series with the input to limit the current to –1 mA or less. This amount of input current is unlikely to cause any damage. If both inputs are above the upper common mode range, the output is undefined; it could be either VOL or VOH. This affects comparator applications, but normal, negative feedback applications are generally not affected because the upper limit of the input voltage range is the same as output high range (VOH).