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LF356: LF356 offset problem when building peak detector circuit

Lai Hai
Intellectual 685 points

Part Number: LF356
Other Parts Discussed in Thread: LF353

Hello everyone,

I am building a peak detector circuit as shown below, but the output is off base line + 1V, is there any way to remedy this?

The power supply for LF356 is +/- 15V.
Thank you,

Hai Lai

  • Former Member
    0 Former Member

    Hi Lai,

    Thanks for your question.  I have a couple of follow up questions for you.

    1. Just to be clear, are U1A and U2A the LF356 device?

    2.  When you say "the output is off base line + 1V," do you mean the peak detector or the analog output to the ADC?  Any type of wave forms or further information you could provide here would be really helpful.

    Regards,

    Daniel

  • 0 in reply to Former Member
    Intellectual 685 points

    Daniel Miller56 said:

    Hi Lai,

    Thanks for your question.  I have a couple of follow up questions for you.

    1. Just to be clear, are U1A and U2A the LF356 device?

    2.  When you say "the output is off base line + 1V," do you mean the peak detector or the analog output to the ADC?  Any type of wave forms or further information you could provide here would be really helpful.

    Regards,

    Daniel

    Hello Daniel,

    1. I was confused, U1A and U2A is LF353.

    2.The output is fed into the ADC.

    Thanks,

    Hai Lai

  • 0
    Guru 140200 points

    Hi Lai,

    have you kept in mind that JFETs show a non-vanishing Ron when being turned-on? What JFETs do you use?

    Kai

  • Former Member
    0 Former Member in reply to Lai Hai

    Hello Hai,

    Thank you for your clarification.  Do you have input and output waveforms?  Is this being done in simulation or is it a real world result?  Lastly, can you please share what the V+ and V- supply values are for the amplifiers?

    Regards,

    Daniel

  • 0 in reply to Former Member
    Guru 140200 points

    Hi Daniel,

    I think it is +/-15V. Lai said so in his first post :-)

    Kai

  • Former Member
    0 Former Member in reply to kai klaas69

    Hello Kai,

    Thank you for catching my mistake.  You are correct.  I would still like to see the wave forms from Hai, if possible.

    Regards,

    Daniel

  • Former Member
    0 Former Member in reply to Lai Hai

    Hello Hai,

    I know we haven't heard back from you in a while.  Has the issue been resolved?

    If not, please let me know.  It would be helpful to see input and output waveforms.

    Regards,
    Daniel