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10-100kHz sine-wave oscillator

Chang Jiang
Prodigy 50 points
Other Parts Discussed in Thread: OPA140, TLV2471, LM318

Hi, 

I've been reading the sine-wave oscillator manual on TI.  I wonder if it's possible to design a wien bridge sine-wave oscillator that can generate 25 to 75 kHz..  Which amplifiers can I use?  It says in the manual that voltage-feedback op amps are limited to a few hundred kHz because of low frequency rolloff.  I only need amplitude of of sine wave below 5V.  What are my options?  Thank you very much!

Best,

Charles

  • 0
    Guru 21975 points

    Charles,

    You should be able to construct a Wein bridge oscillator in the 75kHz range with an op amp such as the OPA140. I don't know what sine wave oscillator manual you are referring to so I will leave it to you to consider the possible details.

    Regards, Bruce.

  • 0 in reply to Bruce Trump
    Prodigy 50 points

    Thank you very much, Bruce!

    The manual from TI I was referring to was on the link 

    http://www.ti.com/lit/ml/sloa087/sloa087.pdf

    Chapter 15 of Op Amps for everyone.  

    This is the circuit I used.  Because I don't have TLV2471, I used LM318 instead.  And I use 10nF and 10kOhm.  Rg 10K and Rf 20K.  The response should be around 1.5kHz.  However, the waveform is very much distorted.  I'll look into the op amp you recommended.  Thank you very much.  

  • 0 in reply to Chang Jiang
    Guru 21975 points

    Charles,

    A more complex circuit with AGC is required to achieve low distortion. This is discussed in the reference that you cite. The LM318 should also be capable of producing reasonably low distortion with a circuit incorporating AGC.

    Regards, Bruce.