Re: Programming Languages

On 3/11/2024 6:21 am, Cursitor Doom wrote:

On Sat, 2 Nov 2024 13:07:32 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
 

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vg4fff$3lok1$1@dont-email.me...

On 2/11/2024 12:01 pm, Edward Rawde wrote:

"Cursitor Doom" <cd999666@notformail.com> wrote in message news:vg3575$3bio0$1@dont-email.me...

You can call me old fashioned, but I still believe there's never been a
more elegant computer language than the original K&R C. You can keep the
rest; I'll stick with that.

>
Having just got back from a vacation I thought I'd give my input to this before looking into whether it's worthwhile getting back
into sinewave oscillators.

>
John May has come up with a much better sine wave oscillator than yours.

>
That's no surprise. I can remember one or two other occasions when I thought I had a brilliant way to do it but someone else came up
with a better way.
I don't specifically mean sinewave oscillators.
>

It also has more components, and I'm not sure that all of them are strictly necessary. Getting deep enough into the design to be
sure where the harmonics are coming from is going to be difficult. I think I'm getting there, but I'm not all that motivated to
put in the rest of the
work.
>
One obvious point is that a FET channel isn't a perfect resistor - as the voltage across it rises above zero it starts looking
more like a constant current diode (and you can buy FET-based constant current diodes).
>
In theory, if you added a second harmonic component to the FET gate drive you could make it look like a resistor over a wider
range of voltage, if the phasing was close enough to right.
>
You've also got the point that when there's a voltage drop across the FET channel, it adds to the gate-to-channel voltage (as has
been mentioned here) and you can cancel that with an in-phase fundamental component

>
The last circuit of my own had both an n fet and a p fet.
I found that by adding a capacitor from one gate to the other (to try to cancel the unwanted signals in opposite phase) I could get
the unwanted gate signal below 100uV. I then had harmonics approaching 60dB down except one at 50dB (I think 2KHz). Not brilliant
but not bad.
>
There are some useful pointers here:
https://sound-au.com/articles/sinewave.htm
In particular where it says "Done properly, a JFET can provide distortion performance that is as good or better than a lamp or
thermistor."
>
Perhaps I'll concentrate on how to make the FET behave as a voltage variable resistor over the widest possible range.
>
I also what to look into what I meant by crud and non crud mode in LTSpice.
This mysterious effect can depend on things such as which specific computer is used and how long is specified before collecting
simulation data.
You can see it in the gate voltage after startup. It looks a bit like a PLL hunting and eventually locking but it doesn't happen at
startup, it happens after seconds.
So I'll need to be able to post some pictures to show that. I'll get to that.

 Hi Edward,
I've been messing around with a real-life WB oscillator - the busted
one I originally posted about. AFAIK, everyone else here has just been
simming them, so I thought it might be useful if I provided some
detail that others may have overlooked.
The thing that stands out in my experiments in replacing the broken
thermistor with a pot and attempting to twiddle for the optimum sine
wave is just how close the waveform has to get to collapsing from
insufficient feedback in order to get a nice sine wave. It's a
knife-edge adjustment to get it right and then of course, with
constantly shifting temperatures it goes out of adjustment again
within a few seconds. But the sweet spot for the best waveshape is
*just* a whisker above collapse.
HTH.

Of course it is.That's why Wein bridges need a non-linear element that can be adjust to get the gain exactly right and keep it there.

Is there an easy way to remove a DC offset from a simulation trace so that my n and p gate signals can be superimposed after
startup?

There is but Cursitor Doom doesn't know it.
--
Bill Sloman, Sydney