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AMC1302: What is the reason for the phase difference between VinAMC and VoutAMC?

Yi-Hsuan Tsai
Prodigy 110 points
Part Number: AMC1302

Tool/software:

Hi everyone,

I am reading page 57 of Ti's Engineer's Guide to Isolated Signal Chain Solutions and I don't understand why the waveforms of VinAMC and VoutAMC have a 180 degree phase difference.

I would like to know why.

Thanks.

 

Best regards,

Yi-Hsuan Tsai

  • 0
    TI__Expert 8455 points

    Hi Yi-Hsuan,

    Thank you for the question. I will look into this and get back to you shortly.

    Best regards,

    Eva

  • 0 in reply to Eva Mason
    TI__Expert 8455 points

    Hi Yi-Hsuan,

    It is because the positive input is being pulled up to 1V at all times and the input current is amplified on the negative input to swing the full-scale range. This causes the 180-degree phase shift shown on the output. 

    Best regards,

    Eva

  • 0 in reply to Eva Mason
    Prodigy 110 points

    Hi Eva,

    Thanks for your reply.

    The level liftng and signal amplification you mentioned are consistent with my understanding, but I still don’t quite understand the phase part.

    My current feeling is whether the waveform of VinAMC is wrong(phase or amplitude value)?

    I feel that VinAMC and VoutAMC should be in phase?

    Below is my calculation formula.

    If mine is wrong, can you tell me if there is any misunderstanding, or can you help me understand the relationship between phase shift more clearly, thank you.

    Best regards,

    Yi-Hsuan Tsai

  • 0 in reply to Yi-Hsuan Tsai
    TI__Expert 8455 points

    Hi Yi-Hsuan,

    In your calculations you show the signal is reversed as an effect of the level lifting and amplification which would also appear as a phase shift. 

    Best regards,

    Eva