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LT6233 Simulation

Category: Hardware
Product Number: LT3233
Software Version: No

Hello,

I'm a beginner. I wanted to do a simulation with LTspice my electronic circuit with a small signal (about 2 µV peak to peak)

But with only 1mV (1kHz) I have an offset (about 32mV), do you know how to remove this offset voltage ?

Thank you for your helps

Regards

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  • Hi  ,

    I found that LT6233 has Ibias of approximately 1.5uA, this is a current flowing into the both -IN and +IN terminals. If you will try to get the product of R1 which is 22.5K and 1.5uA that is 33.75uA, this is the offset that you are seeing on your waveform.

    I supposed that what you are trying to make is a Unity gain amplifier, if I am not mistaken. in order to preserve the gain of 1, I made the following changes on your circuit.

    I added R3 with the same value as R2 and change R1 to match that of R1 and R2. 

    1st, R3 will keep the gain 1

    2nd R1 will eliminate the offset.

    I also found this document to help you with the non-ideality of the Op-Amps.

    https://www.analog.com/media/en/training-seminars/tutorials/MT-038.pdf

    Perhaps this might help you further with your circuit optimization

    Thank you.

    Regards,

     

  • Hello

    PaulDaria,

    Very good, seems very correct to me but the choice of R1

    2nd R1 will eliminate the offset.

    After the Analog Filter Wizard, I chose to filter a signal lower than 1Hz

     

    And the Wizard give me 2 resitors 23 k and 8.67 k.  

      

    If you modify the value of the resistor (to eliminate the offset), I don't know if the filter will work properly. How can i know ?

    Thank for your answer

    Regards

    Yann DO

  • Hi  ,

    You can try running your schematic in AC analysis. To do that I will recommend watching this video.

    LTspice® AC & Noise Analysis Tutorial | Analog Devices

    It will show you the step by step procedure on how to check the frequency response of your circuit.

    Also, I will suggest starting from the schematic recommended by Analog Filter Wizard and then start fixing for the offset from there.

    In this way you can inspect whether the fix you added affects the frequency response. You may also refer on how I remove the offset from you original schematic for you reference.

    Enjoy and happy simulation!

    Regards,

      

  • Hi PaulDaria,

    Thank you for your advice, I found something much easier but I don't know if it's a good method. I added a decoupling capacity at the output of this AOP

    So I removed the offset voltage. But after this HPF I use the ADC. How to simulate an ADC load ? With resistance ?

    Thank you for your helps

    Regards

Reply
  • Hi PaulDaria,

    Thank you for your advice, I found something much easier but I don't know if it's a good method. I added a decoupling capacity at the output of this AOP

    So I removed the offset voltage. But after this HPF I use the ADC. How to simulate an ADC load ? With resistance ?

    Thank you for your helps

    Regards

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