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INA 128

Tahir Mahmood
Expert 1160 points
Other Parts Discussed in Thread: INA128, INA826

Can I use INA128 instrumentation amplifier with only positive suppy voltage? For example only with +12V supply voltage at pin 7 and connect the pin 4 with ground. Will there be any difference if we use +-12V or only +12V as far as performance is concerned? The differential input coming from the differential sensor is normally positive, if it becomes negative due to some reason will the ouput remain at zero volt?]

  • 0
    TI__Mastermind 25815 points

    Hello Tahir,

    Yes, you can power the INA128 with a single 12V supply. However, you must pay particular attention to the output swing with respect to the input common-mode voltage. The INA128 has only dual supply graphs in the data sheet. To understand the difference, please take a look at the following figure from the INA826 data sheet.


    In this figure, the INA826 is operating with a single supply. Notice the output swing depends on the supply voltage, gain, and reference voltage.

    If you give us your reference voltage and gain, we can simulate a similar graph for your application.

    When the operating conditions are changed from those stated in the electrical characteristics table from the datasheet, performance is not assured.  However, on page 10 of the data sheet is states that "Performance of remains excellent with power supplies ranging from +/-2.25V to +/-18V.  Most parameters vary only slightly throughout this supply voltage range..."   Please be aware that changing the power supply voltage to 12V will introduce additional offset voltage according the PSRR specification listed in the data sheet. 

    The output of the device cannot reach V-.  When the input signal becomes sufficiently small, the output will be driven as close to V- as the output stage will allow.  According to the data sheet table this is (V-)+1.4V (min).