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TL074: Input Common Mode Range

Brian Wang0928
Genius 14250 points
Part Number: TL074


Hello,

Customer usually uses the VCC bipolar power (+/-15V) on TL074 for analog input application. However, since they plan to change the power design circuitry, the input bias power for TL074 would be changed to (+18V, -12V) or (+15V and -5V). We'd like to know if these input common ranges are ok for this application or not?

In the datasheet, it said the common-mode input voltage range is +/-11V as minimum value @+/-15V VCC bias power. Does it mean that the dropout voltage of input is 4V, correct? Is this fixed value of 4V no mater what input voltage level, right? and also, how about the output voltage swing range? 

Application: Analog Input Circuitry for VFD.

Regards

Brian

  • 0
    TI__Guru**** 165876 points

    Brian,

    Just translate +/-15V to the new supply voltage that also totals 30V for input and output range.

    Other note is to never directly ground input pins, use a resistor to limit current (1k works well) during power / up down issues. This is also true for +/-15V.

  • 0 in reply to Ron Michallick
    Guru 48395 points

    Hello Brian, the shorter answer is according to the spec table, yes - you need to plan for an input headroom of 4V on each side from whatever supplies you use. The output headroom actually goes down 5V over temp and 2kohm load - that is a lot of wasted headroom on the I/O for this 1978 introduction - also the front page seems incorrect on input swing to +Vcc, surely there is a newer part that would require less wasted supply overhead? Also, that 1kohm suggestion is not universal - That would dominate your noise at 4nV for a wide range of devices - there is a very good concern on what to do there, but 1kohm always is not the answer.