| Electronics > Projects, Designs, and Technical Stuff |
| Analog circuit analysis discussion – Colpitts oscillator |
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| AnneRanch:
OK, gentlemen apparently my "spicy" initial comment did not take. Please read my posts. I have no issues with the circuit oscillating. However I cannot keep up with "adjust this and that" posts here, do my stuff and "honey-dooes". I have modified , annotated the TI circuit to match the book and changed some values. Attached. Perhaps I need to post SPECIFIC questions to get the discussion going in direction I was initially after. From the TI book - they determine the ratio of C2 / C3 experimentally as .47 from that I get the real combined value of C2/C3 - standard Colpitts calculation for oscillator frequency Then there is a lengthy calculation involving C1 They use the initial C2C3 /C2+C3 AKA standard frequency value.... My question is - where did the C1 calculation come from and WHAT is the function of C1? Cheers |
| ledtester:
--- Quote from: AnneRanch on September 17, 2019, 05:54:03 pm ---Please read my posts. --- End quote --- We are reading your posts. --- Quote ---Perhaps I need to post SPECIFIC questions to get the discussion going in direction I was initially after. --- End quote --- That's always a good thing to do on an internet forum. --- Quote ---From the TI book - --- End quote --- What TI book??? --- Quote ---My question is - where did the C1 calculation come from and WHAT is the function of C1? --- End quote --- I don't see a C1 designation on anything you've posted in this thread. |
| AnneRanch:
My question is - where did the C1 calculation come from and WHAT is the function of C1? Per TI C1 is AC bypass of R2 C1 = 300 pf - value chosen to avoid self resonant frequency near 90 MHz |
| duak:
Curiouser & curiouser... I'm also having trouble with the reference designators, the Spice model & your questions. Is the schematic posted mayhaps not what is desired? Also, the schematic looks oddly like a regenerative receiver. ie., antenna on the left, headphone on the right and a control that will vary emitter current. |
| MagicSmoker:
The OP doesn't deserve help, I've concluded. Not only because the questions asked are nonsense (re: the non-existent C1), but mainly because of this gem of a thread: https://www.eevblog.com/forum/repair/464-delayed-sweep-switch-worn-out/ Keep demanding we help you for free and see where that gets you. |
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