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Problems with Royer oscillator and an aircore transformer

Revala

Jun 17, 2015
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Jun 17, 2015
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Hello,

I have been experimenting with different types of oscillators for a while and recently I've been stuck on a royer oscillator. In the simulation I can generate oscillations, but when I assemble the oscillator in real life, no signs of the desired result appear in the secondary circuit.
I attached a picture of the schematic and the .asc file, to this thread. The secondary (high voltage) circuit has been removed because when it is added to the circuit in the simulator, the circuit ceases to function. In real life the secondary coil isn't attached to anything.
The transformer I'm using has an air core, since I'm trying to produce oscillations in the radio frequency range.
I would be very grateful, if someone can point out the mistakes I'm making ang give advice on how to create the secondary circuit in LTSpiceIV without getting error messages or supressing the oscillations, by grounding the secondary coil

Thank you,
Revala
 

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duke37

Jan 9, 2011
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My thought is that you do not have swufficient base drive. Either use a centre tapped drive winding with centre tap to ground or place diodes across the base/emitters of the transistors.

The diode circuit is described in the Mullard transistor circuit book. It allows the base to be driven positive and limits the base negative voltage.
 

dorke

Jun 20, 2015
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Jun 20, 2015
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Hello,


The transformer I'm using has an air core, since I'm trying to produce oscillations in the radio frequency range.

Thank you,
Revala

Shouldn't the transformer work in saturation?
For that you need a ferromagnetic core not an air-core..
 

duke37

Jan 9, 2011
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As I understand it, the transistor current rises until the transistor runs out of breath! Then the collector voltage rises and the opposite transistor is turned on.
An iron core may saturate first or the transistor gain will drop first. In any case, with sufficient loop gain, the circuit should oscillate - assuming the phase is connected correctly.
 
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