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OPA549: parallel connection of three or 4 operational amplifiers for higher currents

Part Number: OPA549
Other Parts Discussed in Thread: OPA454, OPA462
In the OPA549 Datasheet is an example of two parallel operational amplifiers which together can reach currents up to 20A. 


For a test setup, I need a fast, modulatable voltage source with a load capacity of up to 30 amps. How would it best be possible to operate three or four OPA549's in parallel?


  • This is, how the datasheet proposes how to connect two in parallel. 

  • Hi Nathan,

    Q: I need a fast, modulated voltage source with a load capacity of up to 30 amps

    What is the modulated voltage and frequency in your application? what is low and high temperature operating environment?

    I would not recommend to parallel 3-4 op amps for increased output current. It may work, but I am also concerned about interaction among the power amps.  

    Please let us know your design or application requirements and we will see what is the best design options to meet the requirements. 

    Best,

    Raymond

  • the voltage source is to serve as a test power supply for sensors and actuators in the automotive sector. It is necessary to test the behavior of these devices under different voltage levels, for example in the event of brief overvoltage or incorrect polarity. Some actuators under test use up to 30 amps.

  • Hi Nathan,

    OPA549 is unable to meet your application requirements per the datasheet specification. Without going into details of the parallel op amp output configuration, heat dissipation etc., the op amp's slew rate itself is unable to meet the application requirements. In addition, it has Vout compliance issues as well, and the output voltage range is from -14V to 56V, which is outside of OPA549 max. voltage operating range.

    I think that you may need high voltage op amp, like OPA462 or OPA454 + class AB output stage to meet the driving requirements.  If the output voltage does not have to drive below ground, then there may be simpler solutions. 

    If you need further assistant, please let us know.

    Best,

    Raymond

  • Hi Nathan,

    looks like you want to build a Load Dump Simulator?

    Kai

  • Yes, something similar, but we can't use commercial Load Dump Simulators. 

  • Yes, something similar, but we can't use commercial Load Dump Simulators for our purpose.

  • Hi Nathan,

    In the figure above, the output time response is shown. What is the input requirements for the driver? So far, the application requires

    1. biquadrant power output

    2. High voltage and driving current (from op amp perspective)

    3. high BW and high slew rate

    Since the output requirements look like On/Off states, have you thought about the following driving configurations. 

    1. Use a programmable power supply that can source up to +60Vdc, 30Adc. 

    2. Use a programmable power supply that can sink down to -15Vdc, 30Adc (revserse the polarity of the high current positive power supply from step 1, you may use the same type of power supply in step 1.).

    3. Use a solid state relays or mosfet switches to control the output On/Off states. The setup resembles DPDT toggle switch at its output stage. 

    The above configuration will work, except it may have a tough time to control the On/Off transition period under 1usec precisely, which the application may require high speed DC power supplies to meet the requirements. Also, it has something to do with in your output R and C time constant. If the RC time constant is <1usec, then it will work well. 

    Anyway, please let us know if you need further assistant. The above configuration tend to be bulky, but it will work a reasonably well, if there are no time On/Off transition issues at a load. 

    Sure, you may design the state machine with high current type of power amplifiers, but it is difficult to find power amplifiers to meet the BW, output voltage and current requirements all in one chip. 

    Best,

    Raymond