My design is found in the link below. I've breadboarded it and it functions. I was wondering if there are any flaws in it.
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- 1\$\begingroup\$ It is worth noting that the output amplitude will vary significantly based on the β (hFE) of the left-hand NPN, which varies quite a lot between parts and even between individual transistors. With β=150 you'll already start to see some distortion as the BJT goes into saturation, and with β=200 it'll heavily clip. You'll likely want to make the base resistor variable so you can adjust the base current to compensate for this variation. A potentiometer with a max resistance of 470-750kΩ would do the job. \$\endgroup\$Polynomial– Polynomial2025-12-11 16:57:57 +00:00Commented 17 hours ago
- 1\$\begingroup\$ Well, sure. But flaws with respect to what? In other words, what do you want out of it, what do you consider an "improved" oscillator? || @Polynomial hFE is not one I would think to flag here: the arrangement with [collector resistor] - [voltage offsets] - base resistor] (of comparable value) - [base-emitter to ground], gets well-defined DC bias for hFE > 10 or so. Exact conditions vary with amplitude, but that's a given with diodes in the loop; therefore, the concern reduces to the above. \$\endgroup\$Tim Williams– Tim Williams2025-12-11 17:29:28 +00:00Commented 16 hours ago
- \$\begingroup\$ Have you any actual reason why do you prefer a design which depends heavily on differences between purchased components of the same type? You could get more predictable behaviour with other oscillator circuits. What kind of improvement results for the function or other things do you miss most urgently? Do you for example want microwave range output? Or 1 kW output power? Or human voice like output? Or what? \$\endgroup\$oneprivate– oneprivate2025-12-11 17:32:51 +00:00Commented 16 hours ago
- \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$Community– Community Bot2025-12-12 06:32:21 +00:00Commented 3 hours ago
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the way it's drawn makes it confusing, at least to my eyes.
redrawn to show the core part of the oscillator in a way that I think would make it easier to make a mental model of it:
- green .... output at collector
- orange ... node after first diode
- red ...... node after second diode
the limit-cycle amplitude of this oscillator, as typical, is determined by a nonlinear element - which includes the transistor's current gain. as mentioned in the comments, it'll have miserable reproducibility - both part-to-part and over temperature. interesting circuit nonetheless.
