why doesnt this circuit oscillate

Posted on Feb 5, 2014

Used buba oscillator and it didn`t oscillate in the begining. first thing you should check the basics. a little error in cap, res and inductor values makes a huge difference. try calculating the component values with multimeter and i bet cap value wont be exact and if you are using 5% tolerance resistors then what can i say. use good capacitors like tantalum and 1% or 0. 1% resistors and use a pot

why doesnt this circuit oscillate
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to precisely calibrate you gain and 180 degree shift. ceramic capaciotrs wont be good in this case. Strictly spoken, both statements seem mutual exlusive. You would need an ideal current source to represent the said transfer characteristic with an RLC series circuit and the RLC circuit as shunt. Obviuosly you should show a circuit. Assuming you actually insert a transfer function of the said type in an inverting feedback path. Then the 180 ° phase would be varied over 90 to 270 ° maximum, thus never touch the oscillation condition. I am no sure what software you are using to simulate this circuit. but if its possible can you give some initial values to your nodes then give one rail value to your output and the complementary rail value to the base. also try simulating with some transient noise enabled. The transistor in the shown circuit won`t oscillate for the simple reason, that it misses a DC bias. In this case, you don`t need to think further about fulfillling the oscillation condition. The other point is that a transistor isn`t an ideal inverting amplifier. It has additional parameters, e. g. input and output capacitances. Thus I won`t exclude, that the circuit can possibly oscillate after adding a bias network. But if so, it`s not due the RLC feedback allone. * The transistor usually needs a certain amount of bias current in order to get the action started. The bias level needs to be adjustable, hence a potentiometer...

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