Today I Created a basic Colpitts Oscillator Circuit using 2n3904 npn transistor the circuit diagram is given in attachments and when I saw the output I got a Distorted sine wave.I haveu 2,1nF acitors and a1mH inductor as the tank circuit and a 0.1uF c is used to fed back output signal to the base of the transistor. Now the interesting thing is though the output sine Wave is distorted,the input sine Wave looks fine(yellow waveform is input and purple waveform is output) .Please help me getting over this issue and it would be great if someone explains me why this is happening

 

→ try a 1k to 200k resistor in series with LC to Base --and/or-- lower the coupling capacitor --and/or-- increrase the capacitor the feedback goes (e.g. ground a grater share of the feedback)
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► FALSTAD agrees with your setup ◄
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? never seen 2.1 x 10ⁿ capacitor

2,1nF capacitors

~about Capacitor marking codes

 

→ try a 1k to 200k resistor in series with LC to Base --and/or-- lower the coupling capacitor --and/or-- increrase the capacitor the feedback goes (e.g. ground a grater share of the feedback)
__
► FALSTAD agrees with your setup ◄
-----
? never seen 2.1 x 10ⁿ capacitor


~about Capacitor marking codes

@ci139
Allow for some typos and translation: "I haveu 2,1nF acitors" becomes "I have two 1nF capacitors."

 

thanks for translation TK ~\ -.-

Modified the osc circuit to lesser distrotion (i donno if it's Colpitt's or not)
about ::

• bootstrapping
  • https://www.petervis.com/Radios/bootstrapping/transistor-bootstrapping.html
• RF osc.-s
  • http://users.cecs.anu.edu.au/~Gerard.Borg/engn4545_borg/transistors_LO/transistors_LO.html
• partial-collector feedback
  • (the voltage divider @ collector → ) → → → **
    is a random possible way to tune to trg. //// it actually shows that well tuned circuit overamplifies the outp in any case -- notice the resistor and grid changes in between steps //// even the Op-Amp Quadrature oscillator (pg.4) requires automatic gain control to avoid clipping off the tops . . . but we always can extract our sine where it is the sine **
• collector feedback, bootstrapping
  • https://wiki.analog.com/university/courses/electronics/text/chapter-9

 

EDIT:

Please help me getting over this issue and it would be great if someone explains me why this is happening

It is right, good behavior of oscillator, because tank continuously loses energy, but transistor, every period, adds new portion of energy.
Due to high (about 100) gain of transistor, that portion of energy is too big and forms step in bottom of sine.
Problem can be solved by placing resistor between emitter lead and ground.
Picture above shows good sine, when gain of amplifier is about 3 (10k / 3k).

 

why this is happening

the question is always "what (is it)" or "where (there is - it is so)" . . .

as the Base is apx. at the same phase with the Emitter -- your 100nF allows at favorable conditions the LC tank to "discharge"


((( I.C2 has spikes /// I.C5 has -90deg rotated Z-s )))

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fuzzy//"intuitive" Quick fix (( C4 is not verified to make it better -- was added in a hope it improves the transit of the neg. half-cycle ))
? but it might have a jitter in it ( or might be due th pixel-quanted PC-display ) ?