SBOA508 January   2022 INA818 , INA819 , INA823 , INA849 , OPA2392 , OPA391 , OPA392 , OPA396 , OPA397 , OPA3S328

 

  1.   Trademarks
  2. 1Single N-FET or P-FET vs Complimentary N-P-FET Input Stage Limitations
  3. 2Example 1: Output Swing Limitation from VCM in an Op-Amp for Low Side Current Sense
  4. 3Bipolar and CMOS Output Stage Topologies and Output Swing Limitations
  5. 4Example 2: Output Swing Limitations With Instrumentation Amplifiers
  6. 5Summary
  7. 6References

5 Summary

In board-level design, it is important to recognize amplifier input and output stage limitations. Different amplifier input and output stage topologies offer different operating common mode voltage and output swing voltage ranges, respectively. Single supply mode of operation sometimes offers challenges with respect to keeping VCM within the linear operating range on the low end. Choosing a device with VCM range extending below ground or using a negative charge pump to lower the negative supply below ground can help resolve such issues. Conversely, having an expected output voltage value beyond the data sheet output swing specified limits will degrade output accuracy and should be avoided. If selecting an amplifier with a closer to-rail output swing is not an option, then parameters such as the gain of the circuit and supply voltage range can be adjusted to overcome output swing limitations.

Table 5-1 New Device Recommendations
Device Description
OPA391 Micro-power (24 μA), ultra-low bias (0.8 pA), e-Trim™ rail-to-rail op-amp
OPA392 Wide-bandwidth (13 MHz), ultra-low bias (0.8 pA), precision (10 μV), e-Trim™ rail-to-rail op amp
OPA3S328 Wide bandwidth (40 MHz), low bias (10 pA), zero-crossover dual op amp with integrated switches in a tiny package
INA819 Low power (350 μA), low noise (8 nV/√Hz), precision (35 μV), 36-V super-beta input instrumentation amplifier available in tiny package
Low power (350 µA), precision instrumentation amp with ±60-V overvoltage protection (gain pins 2, 3)
INA849 Low power (350 μA), low noise (8 nV/√Hz), precision (35 μV), 36-V super-beta input instrumentation amplifier with +/-60V overvoltage protection available in tiny package
INA823 Low power (180μA), precision (100μV), wide supply range (2.7-36 V) instrumentation amplifier with below ground input range (150 mV) and +/-60V overvoltage protection