SBAA631 January   2025 DAC80508 , INA592 , XTR111 , XTR300 , XTR305

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Analog Output Module Specification
  6. 3Analog Output Module Structure
  7. 4Multi-Channel Output Architectures
    1. 4.1 Fully Integrated DAC Architecture
    2. 4.2 Low Voltage DAC Plus an Output Buffer
    3. 4.3 Track and Hold Multiplexed Output
  8. 5Single-Channel Output Architectures
    1. 5.1 Fully Integrated DAC
    2. 5.2 Low-Voltage DAC Plus an Output Buffer
    3. 5.3 Pulse-Width Modulation Plus a Buffer
  9. 6Output Buffers
    1. 6.1 Unidirectional Current Buffer
    2. 6.2 Bidirectional Current Buffer
    3. 6.3 Voltage Buffer
    4. 6.4 Combined Voltage or Current Buffer
  10. 7Summary
  11. 8References

6.1 Unidirectional Current Buffer

When a source current buffer is required, a unidirectional current buffer is used. A dual-op amp is a straightforward choice which allows a low-cost low noise implementation. For this implementation op amp U1 needs to allow input to the negative rail, while U1 allows input to the positive rail, the op amps are powered by vsup, which is typically 24V, so high voltage low-offset op amps are required. TLV9302, and OPA2990 are a couple of good options for this circuit. In addition a 3 precision resistors are needed. More design details about this circuit can be found in Programmable, Two-Stage, High-Side Current Source Circuit.

Unidirectional Current Buffer Unidirectional Current BufferFigure 6-1 Unidirectional Current Buffer

The other implementation is using XTR111, which offers more integration, output disable option, and output failure diagnostic feedback signal. XTR111 requires only one single precision resistor and has maximum offset in the 1mV range, and works up to 40V supply.