Use AD8037 to make a Full-Wave Rectifier but failed

Discussion in 'General Electronics Chat' started by PSIR, Apr 29, 2008.

  1. PSIR

    Thread Starter Member

    Apr 23, 2008
    29
    0
    Hello everyone :

    Please see the attached file AD8036_37.doc. This is my circuit. I according to AD8036/37's datasheet page 19, Figure 12. Full-Wave Rectifier to made the same circuit.

    But as soon as I input sinewave signal to the circuit. The AD8037 start to getting heat, and power voltage also drop, circuit current also to raise.

    If I remove the input signal, everything turned to normal. I don't know why the reason is. Does anyone who has experience in AD8036 or 37?
    Could you help me to make the Figure 12. Full-Wave Rectifier. Thanks.

    Many Regards

    PSIR
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    The opamp is designed to use a maximum power supply of +/- 6 Volts.
    How much are you giving at the input?
    The schematic uses the lower clamping connection.

    Greetings,
    Bertus
     
  3. PSIR

    Thread Starter Member

    Apr 23, 2008
    29
    0
    As the circuit shows. I gave +/- 5 Volts to the AD8037 and input signal is 1Vp-p.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Do you have bypass capacitors between ground and +Vs and -Vs as shown in the datasheet? If not, you may have some very high frequency oscillations going on that you can't see on your O-scope. You don't show these caps in your schematic.
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The datasheet recommends 140 ohm feedback and input resistors to avoid oscillation. Yours is much higher.
    The datasheet says that an AC8037 is stable only with a gain of 2 or more. Your circuit has a gain that is less.
    The schematic of the full-wave recitifer contradicts the above statements.
    It shows two supply bypass capacitors for each supply.

    I hope you didn't make this high frequency circuit on a breadboard.
     
  6. PSIR

    Thread Starter Member

    Apr 23, 2008
    29
    0
    Dear SgtWookie and Audioguru:

    I appreciate your help very much. I certainly not only didn't connect bypass capacitors(0.1uf and 10uf)between ground and +Vs and -Vs but also made this circuit on a breadboard.

    Then I made this circuit with the essential component on a experiment board by soldering-iron. It works, it can rectified high frequency up to at least 1MHz.

    Many Thanks
     
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