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OPA627: Output Voltage at Supply Votage=5V

Part Number: OPA627
Other Parts Discussed in Thread: TEST, TINA-TI, OPA828

Dear all,

I would like to ask a question about output voltage range.

When the output voltage range of the OPA627 was confirmed, only the case where the power supply voltage was ± 15 V was described as follows.


Our customers are going to use with output voltage 5V.
At this time, what is the output voltage if the measurement conditions are the same as the above figure?
I believe that when the power supply voltage is 5V, the output voltage min will be ± 1V.

Best Regards,

Y.Ottey

  • Hi Y.Ottey,

    The data shown in the table above is specifying the output voltage ranges, which is limited to the common-mode input voltage ranges. Within the input and output ranges, the op amp will be operating linearly, see the captured image below.

    If you are using the op amp for sourcing 5V output (as voltage regulator) with the test circuit shown in the datasheet, the circuit should get 5V output + very small voltage errors. The small voltage errors are contributed from input offset voltage, 1/f, thermal noises and gain of your circuit. The current errors from the part is negligible. The contributed voltage errors will be in mV range or less, depending on your circuit. It will not have +/-1V range. This assumes that your circuit is operating within the specification of the part regarding to its output current, temperature ranges, and stability of the op amp vs. input and output frequency responses. 

    Best,

    Raymond

  • Hi Raymond

    Thank you for your reply.

    "Our customers are going to use with output voltage 5V.
    At this time, what is the output voltage if the measurement conditions are the same as the above figure?
    I believe that when the power supply voltage is 5V, the output voltage min will be ± 1V."

    I'm sorry, the above question is incorrect.

    I would like to know the output voltage range when the power supply voltage is 5V.

     

    Regards,

    Y.Ottey

  • Hi Y.Ottey,

    the TINA-TI simulation yields a typical output voltage of +/-2.8V at +/-5V supply voltage and 25°C. The minimum output voltage will be somewhat lower. I think your assumed minimum output voltage of +/-1V over the specified temperature makes sense.

    Remember that the OPA627 was developed for a supply voltage of +/-15V. It's no rail-to-rail OPAmp.

    Kai 

  • Hi Y.Ottey,

    Agreed with Kai's comments for 5V rails. This is not Rail-to-Rail Op Amp. The common mode voltage is approx. 2.2V from 5V power rails. 

    Your customer may have to increase the rail voltage or change the part, if you want to increase the output voltage range. 

    Enclosed is OPA627 Tina simulation.

    OPA627 with 5V rail.TSC

    Best,

    Raymond

  • Hello Y.Ottey,

    Although the OPA627 will operate with supplies as low as Vs = ±4.5 V, it really is performance optimized for ±15 V supply operation as Kai indicated.

    If you take the OPA627 output voltage swing numbers from the datasheet Electrical Characteristics table which are for Vs = ±15 V, you can get an approximation of what it will be with Vs = ±5 V. Using the TA = 25°C numbers for the output range ±11.5 minimum and ±12.3 typical, we see that in that case the minimum swing is ±3.5 V, and typically ±2.7 V from the supply rails. Therefore, the approximate output swing with ±5 V supplies would be about ±1.5 V minimum and ±2.3 V typical.  

    The OPA627 is a legacy, very high-performance JFET input op amp developed in a time when output swing to the rails wasn't in demand. That feature became more of a reality with the CMOS op amps. If you need a high precision JFET input op amp whose output will swing within about a volt of the supply rails see the next generation OPA627 replacement, the OPA828:

    http://www.ti.com/lit/ds/symlink/opa828.pdf

    Regards, Thomas

    Precision Amplifiers Applications Engineering