Ocillators Part 1 RF

Tutorial 2. First of all this tutorial will be devided into two pieces. 1st a few RF oscillators. So an oscillator is an electronic device that will create a fluctuation then feed it back into the input with an opposite phase and amplify it until it can create a stable fluctuating wave that will go from positive to negative following a sinusoidal law. Now there are other type of oscillators that will create different waves like square,sawtooth,ramp,triangle but ill try to cover it all in the second part. 1. The first oscillator is called a hartley oscillator and is an LC tuned circuit . The distinguishing feature of hartleys oscillator is the single capacitor connected in parallel with two inductors in series. And the feedback for the oscillations is taken from the center tap of the two inductors. 2. The second and the third circuits are whats knows as a Colpitts oscillator (with a few elements rearranged). Its basically an inverted hartley oscillator due to the fact that the feedback is being taken from a voltage divider made out of two capacitors which are in parralel to the inductor. 3. The third one is called a ring oscillator and is composed from a number of not gates whose output oscillates between two vo.tage levels,representing true or false.they are attatched in a chain and the output of the last gate is fed back at the input of the first (see the feedback here ;) ). 4. Ah finally the Wien bridge oscillator (the most hard to stabilise even somethimes incandescent bulbs are being used as a power detector to regulate the oscillation) this is the only oscillator that is different from the others. Why? Because it contains no inductors. Its composed from an RC circuit rather than an LC circuit. Nevertheless if perfect balance is obtained and the gain must be precisely 3 not 3.0000001 not 2.9999999 because the output will either rise into cutoff or will fade away. These kind of oscillators give best simetrical results. The wien bridge in the simulation gives the best amplitude in my opinion followed by the second colpitts oscillator.

published 11 years ago