# Someone please explain the directions of current in Inductor,charging of C1 and C2 during cutoff intitally, during saturation and then in active mode.

#### Ram Chockalingam

Joined Jul 9, 2023
7

#### WBahn

Joined Mar 31, 2012
29,519
Since this is homework help, we can't do your homework for you.

Take your best shot. Assume that this is an exam question and you have no choice but to provide the best answer you can based on your current understanding. Present that here. We can then review it and let you know where you are on the right track and where you are going off the rails.

#### Ram Chockalingam

Joined Jul 9, 2023
7
Sorry this is not my homework, I am learning basic analog electronics on my ownI initially posted this question in the general electronics chat I don't know how it got changed to homework section and I'm not sure how to move this thread to general chat again as I'm new to AAC.

#### WBahn

Joined Mar 31, 2012
29,519
Actually, the same reasoning still applies. You are trying to learn something and the best way you can do that is to do your own best to answer the question first. This forces you to think about what you do and don't believe and the reasoning behind it. That puts you in a much, much better position to benefit from subsequent discussions, especially to the degree that they disagree with your thoughts and reasoning.

Redrawing your circuit might shed some light on things.

I don't know what transistor you are using, so I just picked one. The frequencies implied by your choice of capacitance and inductance would indicate something in a the range of a couple hundred hertz, so a 2N3904 will probably work just fine.

#### Ram Chockalingam

Joined Jul 9, 2023
7
So after C1 develops 0.7V across it's plates (top +ve and bottom-ve) saturation mode is attained and the path through R2 becomes open circuited so now C1 can't develop further voltage in the same direction due to the transistor's BE junction in parallel. Now C1 has to discharge and for that the current in LC circuit has flow in the anticlockwise direction after that no more saturation and R2 path starts conducting again slowly current in the inductor changes direction and later C1 charges to turn the transistor ON in your view of the circuit. Am I right?

#### Audioguru again

Joined Oct 21, 2019
6,454
I think your extremely simple circuit has the transistor saturated (turned on hard all the time).
Most transistor Colpitts Oscillator circuits on the internet have the transistor biased properly so it is a good amplifier like this circuit:

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