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TL074-EP: Bias Supply Topolgy For TL074

Brian Wang0928
Genius 12980 points
Part Number: TL074-EP
Other Parts Discussed in Thread: TL074, , TL074H, OPA4991-EP

Tool/software:

Hello Team,

Here is the analog output application with TL074QDREP in motor drive. The bias supply of TL074QDREP is 0V(VCC-) and 15V(VCC+). With this configuration and below circuitry, When pin10 is 0V, the output of TL074's pin8 is 12V. However, when VCC- pin is changed form (0V) to (-1V) and the VCC+ is 15V, with that dual bias power the OPA's output is normally. We are curious why it doesn't work with single bias power. Could you help to check on this issue! Thnak.s 

 

  • 0
    Guru 286090 points

    These voltages are outside the common-mode input voltage range. The TL074-EP requires a hreadroom of at least 4 V to both supplies.

    The TL074H has rail-to-rail outputs and allows voltages down to VCC− at the inputs.

  • 0
    TI__Mastermind 22397 points

    Brian, 

    I agree with Clemens, in that you are running outside the common mode range.  When violating the common mode range the amplifier will not function like a normal op amp and the output can be unpredictable.  The recommended replacement OPA4991-EP has rail-to-rail inputs, so it would allow common mode voltages from the negative supply to the positive supply.

    best regards, Art