Colpitts Oscillator

211

04:59:41

Basic Colpitts oscillator from Wikipedia.  
To get this circuit to oscillate, we start it switched on in the simulation and time base to 10 ns/sec.  Note.. Takes 20 sec or so to warm up and start oscillating.

published 10 years ago

giomix

10 years ago

Hello, why ground is placed there at +6 volt ? If I place it at minus of vcc generator as usually wave is up of 6 volt

WTFCircuit

10 years ago

Because to start it needs -6V

ferlop

10 years ago

If you ground the minus supply it still oscillates. I just did it.

thebugger

10 years ago

He's right. You need to ground the negative part of the power supply and decouple the output. It doesn't need -6V, although it may work this way it's not recommended.

ScritchWuff

10 years ago

As long as the relative potential between top and bottom is +6, it doesn't matter where you put "ground". I just wanted it to oscillate about zero. :)

ScritchWuff

10 years ago

But, I can also put "ground" on the negative side and decouple.

ScritchWuff

10 years ago

One thing I haven't figured out.. If I save the circuit with the switch open, then close the switch with everything at zero, there is of course a voltage transient at t=0+ because of the inductor and things seem to get into a wild decaying oscillation state. Don't know if that's just a property of this oscillator or maybe an inaccuracy in the simulation.

ScritchWuff

10 years ago

Now displaying output vs base/emitter voltage. Now I understand how this thing works. :)

ScritchWuff

10 years ago

Figure out why when you start the oscillator by closing the switch, it doesn't oscillate. It actually does. The issue is that it takes a very LONG time to charge up the caps. Many orders of magnitude, as in milliseconds instead of nanoseconds. So if you wait 1000 years, or dial the timebase back, it will eventually stabilize.

Addramyrz

10 years ago

Three Shakes

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