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LM258A: output distortion issue

Tess Chen
Intellectual 2675 points
Part Number: LM258A
Other Parts Discussed in Thread: TEST2, OPA2333, , LM258, LM358LV

7026.test2.TSC

1258.Test1.TSC

Hi Team,

Application is to amplify AC HART FSK signal and add DC bias for output. But the output has distortion issue with LM258A that you could refer to the screenshot below. And the issue could be solved by replace by OPA2333. Simulation are also work with OPA2333 but not LM258A.  Please refer to attachment test1 and 2.  What will cause the difference between OPA2333 and LM258A? And does the circuit has any improvement to be made? Thanks.

V+ yellow, V- blue and Vout purple

  • 0
    Guru 47545 points

    Well Tess, this LM258 is almost from the dawn of time (1976) before anyone was thinking about RR I/O - you are running into I/O headroom limits likely, 

  • 0
    TI__Guru*** 140186 points

    Tess,

    For LM258 it is important to check VOL (while sinking current) and VOH (while sourcing current).  In this case, the VOL (while sinking current) is the limiting factor. See data sheet figure 47. To get the maximum output swing, the output should always be sourcing or always sinking current. That would be very wasteful in this case due to the low impedance load.

    The lowest cost upgrade that will makes thing much better is LM358LV.