1.2V-25V/10A Adjustable Power Supply Using Power Op-Amp

  • Rajkumar Sharma
  • 27925
  • easy
  • Tested

This is a small size power supply based on OPA549 power op-amp that provides output voltage 1.2V to 25V with 0 to 10A adjustable current limit. Two onboard trimmer potentiometers provided to adjust the voltage and current, LED D1 is over temperature indicator. The circuit works with input supply of 30V DC and logic supply 5V DC. IC requires large size heat sink to work with full 10A current range. Screw terminals for input and output connections are provided. The OPA549 is a low-cost, high-voltage/high-current operational amplifier ideal for driving a wide variety of loads. This laser-trimmed monolithic integrated circuit provides excellent low-level signal accuracy and high output voltage and current. The OPA549 operates from either single or dual supplies for design flexibility. The input common-mode range extends below the negative supply. The OPA549 is internally protected against over-temperature conditions and current overloads. In addition, the OPA549 provides an accurate, user-selected current limit. Unlike other designs which use a “power” resistor in series with the output current path, the OPA549 senses the load indirectly. This allows the current limit to be adjusted from 0A to 10A with a resistor/potentiometer, or controlled digitally with a voltage-out or current-out Digital-to-Analog Converter (DAC). The Enable/Status (E/S) pin provides two functions. It can be monitored to determine if the device is in thermal shutdown, and it can be forced low to disable the output stage and effectively disconnect the load. The OPA549 is available in an 11-lead power package. Its copper tab allows easy mounting to a heat sink for excellent thermal performance. Operation is specified over the extended industrial temperature range, –40°C to +85°C.


  • Input Supply 30V DC
  • Logic Supply 5V DC
  • Output 1.2V to 25V DC
  • Load Current Limit Adjustable 0 To 10A
  • Thermal Shutdown LED Indicator

A programmable source and sink power supply can easily be built using the OPA549. Both the output voltage and output current are user controlled. See Figure 12 for a circuit using potentiometers to adjust the output voltage and current while Figure 13 uses DACs (refer to datasheet). An LED connected to the E/S pin through a logic gate indicates if the OPA549 is in thermal shutdown.

Adjustable Current limit

The OPA549’s accurate, user-defined current limit can be set from 0A to 10A by controlling the input to the ILIM pin. Unlike other designs, which use a power resistor in series with the output current path, the OPA549 senses the load indirectly. This allows the current limit to be set with a 0μA to 633μA control signal. In contrast, other designs require a limiting resistor to handle the full output current (up to 10A in this case). Although the design of the OPA549 allows output currents up to 10A, it is not recommended that the device be operated continuously at that level. The highest rated continuous current capability is 8A. Continuously running the OPA549 at output currents greater than 8A will degrade long-term reliability.


Parts List




OPA549 Datasheet




  • Tibamwenda Anthony

    What exactly is logic supply

    3 years ago
    • admin

      The 5V logic supply is needed to power the logic circuits of the OPAMP and feed the inputs, so you will be able to set the voltage and current. So, in this project, two voltages are needed, an input voltage that will be regulated by the IC and a logic voltage that needed to make the IC work.

      3 years ago
      • Tibamwenda Anthony

        What problem will this project actually address,like what is the background to that problem?

        3 years ago
        • admin

          This project makes possible to control the voltage and current delivered from a 30V/10A source so you will be able to power your device with it. Ofcourse, you will need a 30V DC supply that will be used as the input to this circuit.

          3 years ago
          • Gordon Robertson

            “Of course, you will need a 30V DC supply that will be used as the input to this circuit”.

            Which means you could use a transformer to step down line AC to a lower secondary AC then rectify and regulate the AC to 30VDC using an electrolytic capacitor.

            30V is too high for a 7805 regulator, so I presume a 15 volts zener with an adequate series resistor could be used as a source for a 7805, to get the 5 V reference.

            I am looking at a design using a 24VAC secondary at 5 amps. I don’t need the full 8 amps. The OPA549 can operate from 8 VDC – 60 VDC and I am not concerned if I’m exactly at 30VDC as input. I am more concerned with getting a source for 5VDC from the same secondary without using a dedicated 5V source.

            2 years ago
  • Delip Mehrottra

    I don’t see any regulation loop of any kind,please clarify.

    2 years ago
    • I have attached above figure 10 from the datasheet of OPA549, where you can see the circuit in a better understandable way. You can see there is a 9k resistor going from the output to – input and that’s a negative feedback for the OPAMP which enables it to keep the output in sync with the +input and multiplied by 10. Hope this help you better understand the circuit.

      1 year ago
  • Dmitry

    Hi, how accurate is the current limit setting? And did you try to control Ulim and Ilim with the DAC?

    1 year ago
    • You may replace the current set potentiometer with a precision one. We haven’t measured how accurate this is or check the set values with a DAC, this need to be tested on your end.

      1 year ago
  • how can I buy this OPA 549 board?

    3 months ago
    • please check your email.

      3 months ago
  • Anton

    Hi There. Where and how can I buy this OPA 549 board complete build?

    2 months ago

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