Re: Random thoughts on sinewave oscillators

On Fri, 18 Oct 2024 13:47:02 -0400, Edward Rawde wrote:

"Cursitor Doom" <cd999666@notformail.com> wrote in message
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On Fri, 18 Oct 2024 11:25:19 -0400, Edward Rawde wrote:
>

"piglet" <erichpwagner@hotmail.com> wrote in message
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Edward Rawde <invalid@invalid.invalid> wrote:

>
The circuit below produces a reasonable looking sinewave but the
rise time still seems to be slower than the fall time. It may be
that the amplifier in use is not ideal for this.
>
>

Could that just be second harmonic distortion? You could test the
amplifier by uncoupling the Wien network and injecting test inputs.
>
Elsewhere I think your amplitude control problems could be simply due
to too much gain.

>
Perhaps, but I've not so far been able to get the circuit I posted in
response to Bill to produce a sine wave no matter what I do with the
control loop gain.
It either grows to clipping or dies.

>
That's the main purpose behind having a thermistor or filament bulb in
the f/b path.

 
Sure, but why use thermistors or filaments if you don't have to?
Filaments don't last forever, particularly not if you drop your
equipment, and filaments make me think of something like a 5U4.
I forget when I last saw a filament. House lamps don't even have them
now.
 
I'm trying to make a low cost oscillator which produces the cleanest 1K
Hz sinewave I can get, using only resistors, capacitors and
semiconductors.
 
There are plenty of examples online, but some of them don't seem to
simulate.
Whether that's because they do work in reality but not in simulation is
hard to say.

A real-world oscillator needs some kind of stimulus to start up. This
could be a voltage 'shock' at switch-on or just inherent noise in the
circuitry. JL informs me LTSpice doesn't have such a stimulus unless you
provide it yourself. I suspect that's the main reason you will find
oscillators difficult to get started in simulation.