SBOA441 October   2020 OPA192 , OPA2192

 

  1.   Design Goals
  2.   Design Description
  3.   Design Notes
  4.   Design Steps
  5.   Design Simulations
  6.   DC Simulation Results
  7.   Design References
  8.   Design Featured Op Amp
  9.   Design Alternate Op Amp

Design Notes

  1. Ensure common-mode voltages at the inputs (Vcm nodes) of both op amps are within their Vcm range listed under Electrical Characteristics in the data sheet of the op amp.

  2. Refer to the typical Output Voltage Swing vs. Output Current graphs in the data sheet to account for output swing from rails (Vout nodes) for both op amps.

  3. Resistor mismatch will contribute gain error and degrade CMRR of the circuit.

  4. The buffer offers improved output impedance of the current source nearly eliminating Ifeedback current. This allows the use of smaller resistor values for R1 through R4, reducing thermal noise. Possible bandwidth limitations and stability issues caused by large resistances and parasitic capacitances in the circuit are also reduced.

  5. Special precautions should be taken when driving reactive loads.

  6. A typical design procedure first calculates the gain for a known output current and shunt resistor; then sets R1 and scales R2 through R4 accordingly. This can be an iterative process.

  7. The figures use two OPA192 op amps, but in practice a single chip OPA2192 can be used.