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How to add new component in LT Spice

joniengr

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Hi,
I need to add LM324 or LM224 OpAmp in my schematic. I have searched in the component library. I don't find these components in the existing library of LT Spice.
 

joniengr

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Hi,

Now I have added a new component (LM 224) in the library by creating new symbol from the spice model file. The spice model of LM 224 I have downloaded from the link provided in the post 2.

Here is the tutorial I followed to create a new symbol and then add it as a new component in the library.

LTspice Creating and Working with Symbols

I have designed an inverting operational amplifier with gain of 20. The input signal is 10 mV that should give an output signal 200 mV but in the attached simulation, the output is shifted down by 20 mV. The max and min values are +180 mV and -220 mV. Any idea how to center the output ?
 

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  • Untitled 10 mV to 200 mV.png
    Untitled 10 mV to 200 mV.png
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KlausST

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Hi,

The specified input offset voltage is 3mV typ and 7mV max.
Multiplied with a gain of 21 you get an output offset voltage of 63mV typ and 147mV max.
So with your 20mV you are well within specification.
(Still ignoring offset current, bias current and all offset drifts)

You may compensate by adding subtracting a fixed DC voltage.
Often done by a potentiometer and two resistors at +Vin.
This may improve static offset, but can't improve drift. Additionally it adds offset caused by power supply fluctuation.

If you are interested in better offset performance: look for Opamps with better offset specification.

Klaus
 

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