• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 226 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

LMC6482: LMC6482 as a DIfferential amplifier in my end application for analog current sensing application, I have received...

LMC6482: The offset when input common mode closed to V-, 0v when using single end supply

Jason Shen
Intellectual 1965 points
Part Number: LMC6482


Dears

We have fund a issue when using the LMC6482 as the current sensing amplifier, with single supply(0 - 5V), and input common voltage is very close to ground. the offset is around 20mV (with 10V/V, the output is around 200mV), but this spec is not specified in the datasheet. we have only define the offset when the common voltage in the middle of supply.

So we need your help if we have some data when the  common mode closed to V-. 

Thanks

Jun Shen

  • 0
    TI__Guru 68281 points

    Jun,

    The 20mV "offset" you refer to is NOT a true offset voltage but rather a byproduct of the non-linearity of the output stage. Even though LMC6482 is called rail-to-rail input/output and the input common-mode voltage range of LMC6482 is true rail-to-rail, no linear op amp can swing all the way to its rails at its output as this would require no current in the output stage. If you look at the output range of LMC6482, it is specified around 200mV from either rail - see below.  Thus, if you drive the output to zero, the closest it can get to ground is 180mV, which in the gain of 10 will show as 18mV "offset." In reality, it is simply a voltage 1/10 voltage divider of the output voltage minimum swing.