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LM358: A intergrator of LM358

user5264061
Prodigy 160 points
Part Number: LM358
Other Parts Discussed in Thread: TLV9002, OPA349

I test the intergrator design diagram of LM358. The  input is 5V DC.

But as show below, the output of amplifier  isn't a linear line, and the max output voltage is about 4.3V only.

I don't know why?

As in simulation by multisium, the ouput is a linear line and it's max output can be 5V.

The design diagram:

The shape of output line:

  • 0
    Guru 140200 points
    Hi,

    in the real world the OPAmp cannot work without any resistance in parallel to C1. So, what you see is a LM358 which saturates.

    What is this circuit expected to do? Can you tell a bit more about your application?

    Kai
  • 0
    TI__Guru**** 155896 points

    Hello User,

    The LM358 output only goes to about 3.7V with a 5V supply. The input range is also the same.
    Is your waveform linear from 1V to 3.5V then becomes distorted?

    Try TLV9002 instead, it has rail to rail input and output.

  • 0 in reply to Ron Michallick
    TI__Guru**** 155896 points
    User,

    In this design , it is important the at the capacitors match each other. Simulated caps will match, real world caps, not so much.
  • 0 in reply to kai klaas69
    Prodigy 160 points

    Thanks for your reply,

    I design a board ,there were two different ways of my  power supply.

    The different ways is Battery Power and USB Power.

    Normally, the user can use battery power. As time goes on, the Battery may inter low power mode. User can use USB power to supply the system when the battery in low power mode. I want to design a diagram that it can restart system when a USB power use to replace the Battary power. In order to make sure system restart,  I design the digram like this.

    (The battery power would be turn off when USB be used. And the changing-over diagram I haven't post.)

  • 0 in reply to Ron Michallick
    Prodigy 160 points

    Thank for your repply.

    Today I used OPA349 instead. And the wave shape in scope like this:

    channel 1 : power supply which is 6V DC

    channel2 :  output voltage which have been intergrated