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Following is the proteus design of the oscillator it works fine in simulation .. but not working in hardware.. it doesn't oscillate....!! what could be the reason do i need a voltage signal to kick start the oscillation???
Sometimes an oscillator will not get going, unless it has exactly the right amount of bias (no more, no less) at the transistor/ mosfet / jfet.
Suggestion: install a potentiometer (10k ohm) to adjust the bias.
This appears to be a Hartley type. In the same family anyway.
I made a change or two (in addition to the potentiometer).
I substituted a resistor for the leftmost capacitor. Up until then I was not able to obtain reliable oscillations. For the same reason I used a transistor instead of a jfet.
I don't agree that the circuit works fine, because it produces rather distorted waveforms in simulation. There are tons of better oscillator circuits.
Possible reasons why it might not work in real life:
- FET IDSS/VGSS is too high for the circuit dimensioning. 2N3819 has a rather wide parameter range. Check for sufficient Vds.
- The inductors have too low self resonance frequency respectively too high winding capacitance for the intended frequency range. Check the specification.
I tried to make my original design work but it didn't .. so I sort of played with it, ended up in burning one FET anyhow the modified design worked perfectly on hardware as well as in simulations!!!
Here is the modified one!!
Values were all taken randomly bcz typical formula didn't worked in this design... I can't justify my values mathematically but they are working perfectly and that is what i guess matters
I will appreciate if someone can come up with the mathematical equation to calculate oscillating frequency, it will help future designers as it is a very economical and easy to implement oscillator !!!