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INA293: ELECTRONIC LOAD

ali aykan
Prodigy 110 points
Part Number: INA293
Other Parts Discussed in Thread: OPA188, BUF634A, THS3491

Hi Team,

I want to design an electronic dc load. I drew a test board as in attachment. I have some concerns and questions about the design in schematic.

1. I plan to use INA293 (U1) as current sense amplifier. Is it suitable or should I use rail to rail zero drift amplifier like OPA188?

2. Which single supply amplifier do you advice for higher slew rates as a buffer (U3) for driving linear MOSFET (IXTX200N10L2) (Ciss=23nF)

3. If you have further comment, advice about the general topology and schematic I'll be glad to hear.

Best regards,

Ali

6765.SCHEMATIC1 _ PAGE1.pdf

  • 0
    TI__Mastermind 27870 points

    Hello Ali,

    ali aykan said:
    1. I plan to use INA293 (U1) as current sense amplifier. Is it suitable or should I use rail to rail zero drift amplifier like OPA188?

    You could use either if VLOAD is under under the 15V but the OPA188 would need some more resistors to set the correct gain.  Also you may need the OPA188 used with Dual supply as your input will be limited by the lowest supply voltage.

    ali aykan said:
    2. Which single supply amplifier do you advice for higher slew rates as a buffer (U3) for driving linear MOSFET (IXTX200N10L2) (Ciss=23nF)

    I do not not the best option for this as there are many things to take into account especially with stability in the circuit.  I would attempt to simulate.  C14 is the capacitance directly at the output of U3 which may be an issue.  as driving the 23nF is isolated by R11 and FR1.  

  • 0 in reply to Javier Contreras4
    Prodigy 110 points

    Hi Javier,

    Thank you very much for your reply.  How can I narrow options for a stable dynamic buffer as starting point? Is it suitable THS3491 or BUF634A with a split supply? What do you think about low side gate driver, is it a logical approach?

    Best regards,

    Ali

  • 0 in reply to ali aykan
    TI__Mastermind 27870 points

    Hello Ali,

    You need to look at the whole system for stability.  I would suggest simulating the whole circuit.  The reason is even the MOSFET will impact the stability.  I would start with the circuit you have now.  For stability I quickly do a step response to determine the stability quickly.   https://www.ti.com/seclit/eb/slyw038c/slyw038c.pdf page 65 and 66.

    For the drive I would look at all the specifications you are trying to achieve and the FET you are driving.  I assume all the components you have in your circuit are for help with slew rate and stability?  Are will that be a variable in your system?  I do not think you need split supply as your low of GND should be enough to turn the FET off.