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Simple LC Oscillator

Discussion in 'General Electronics Discussion' started by pidja105, Mar 22, 2016.

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  1. pidja105

    pidja105

    106
    1
    Oct 16, 2015
    Hello,
    I want to build simple LC oscillator but I know where is the input, I don't know where is the OUTPUT for attaching two wires for obtaining frequency.Can you tell me where I can attach that two wires? Thanks!
     
  2. LvW

    LvW

    604
    145
    Apr 12, 2014
    Input? An oscillator does not have any input (just DC supply).
    More than that, there are many different LC oscillator topologies.
    Show us your circuit.
     
  3. pidja105

    pidja105

    106
    1
    Oct 16, 2015
  4. pidja105

    pidja105

    106
    1
    Oct 16, 2015
    http://www.electronicshub.org/lc-oscillator-basics/ on that page LC tank circuit.
     
  5. LvW

    LvW

    604
    145
    Apr 12, 2014
    An LC tank circuit is not an oscillator because of unavoidable resistive losses within the circuit. You neeed an amplifier.
     
  6. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Here is a practical circuit for a Colpitts's oscillator.

    The C in the LC is computed as C1 and C2 in series, in this case 50n.

    The output comes from the collector of Q1.

    upload_2016-3-22_12-27-40.png
     
    Arouse1973 likes this.
  7. AnalogKid

    AnalogKid

    2,371
    661
    Jun 10, 2015
    As shown on the 9th image on the page you linked, the output comes from the output of the opamp.

    ak
     
  8. Colin Mitchell

    Colin Mitchell

    1,417
    312
    Aug 31, 2014
    As soon as you attach the two wires and try to read the frequency, you will load the circuit and it will stop working and you will get NO OUTPUT.
     
  9. AnalogKid

    AnalogKid

    2,371
    661
    Jun 10, 2015
    Not true, of course. The opamp output is a low impedance voltage source designed to provide a signal output to some other circuit or use. Connecting between the opamp output pin and the circuit ground is the best way to observe the oscillator output signal. Another way is to connect a high impedance scope probe across the L-C tank, but this will change the oscillator circuit frequency. If the impedance of the equipment being connected is too low, such as 50 ohms, it can cause the oscillator to stop. However, oscilloscopes or frequency counters usually have a high impedance option.

    ak
     
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