Amplified Hartley Oscillator

Discussion in 'Wireless & RF Design' started by yy.toh@live.com.my, Mar 9, 2011.

  1. yy.toh@live.com.my

    Thread Starter New Member

    Mar 9, 2011
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    I have simulate a hartley oscillator and its ouput is 4nV peak to peak. I need 6V peak to peak, any idea how to amplify it?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Are you sure that your oscillator output is only 4 nanovolts? How did you even find it? Some of the output has to feed back in order for oscillations to continue - that level is certainly not enough.
     
  3. yy.toh@live.com.my

    Thread Starter New Member

    Mar 9, 2011
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    Now I wonder where is the location of the output.

    at base before the coupling capacitor:
    V peak to peak 500mV
    I peak to peak 100mA

    at base after the coupling capacitor:
    V peak to peak 40uV
    I peak to peak 8uA

    at collector:
    V peak to peak 300nV
    I peak to peak 300nA

    The values at collector is smaller than the base, i donno why
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Maybe you can post the schematic?
     
  5. yy.toh@live.com.my

    Thread Starter New Member

    Mar 9, 2011
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    Here is the schematic please suggest.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    I think you are misreading the results of the simulation. You are asking a lot with those 1 ohm resistors. Generally, you make the oscillator and then amplify the signal. Perhaps Multisim will let you use unusual component and values.
     
  7. yy.toh@live.com.my

    Thread Starter New Member

    Mar 9, 2011
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    I think there is no missreading, the readings are directly from the simulation probe.
    The peak to peak values are still in uV even I increased the resistor values.
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    Look at the RMS values. I am not familiar with that simulator, but it looks like the p-p numbers are for ripple.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    [​IMG]

    There is no real feedback there, I don't think it can work. You have one of the coils shorting the power supply, instant smoke. L1 should be going to the collector of the transistor and ground. You will need to dramatically increase the values of the resistors, 2 amps just for base bias (6V/2Ω)?

    Colpitts...

    [​IMG]

    Hartley...

    [​IMG]

    They are more similar that you might first think. The concept is an inverting amplifier with a tank circuit that also inverts the signal. Work on the transistor amplifier a bit more first.

    .
     
    Last edited: Mar 15, 2011
  10. Wendy

    Moderator

    Mar 24, 2008
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    Here is a design I cobbled together. It has never been tested, but I suspect it will work first time. I am allowing the coils to conduct DC through to the transistor, turning what is a problem with your design into an asset with mine.

    [​IMG]

    C2 is a power supply filter cap, and C3 will increase the gain of the transistor circuit. It might be eliminated with improved results.
     
    BlackCow likes this.
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