Sujet : Re: Low distortion sinewave oscillator without big capacitor.
De : invalid (at) *nospam* invalid.invalid (Edward Rawde)
Groupes : sci.electronics.designDate : 05. Apr 2025, 15:17:38
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"Bill Sloman" <
bill.sloman@ieee.org> wrote in message
news:vsqfc3$1emr4$2@dont-email.me...On 5/04/2025 10:12 am, JM wrote:
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:add0vjdh2gcma0n9pfunq76n04cfbkhtnj@4ax.com...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vsnufh$2ou7j$1@dont-email.me...
On 4/04/2025 11:33 am, JM wrote:
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:qq8tujlpciqc2jrd0ibljmjr9pd37ip6hi@4ax.com...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a large
capacitor.
>
You will need to adjust the feedback to suit. Start with a -5 or -6
gain block after the integrator and adjust it's gain until the startup
is clean (no saturation).
>
Here's my version of John May's variation.
>
...
>
Yes, that works but only 120dB down at 4KHz.
I put the damping resistor back to 47k since I don't care what happens during the first few seonds as long as it happens.
If it's necessary to wait one minute for the purest tone, that's fine with me.
>
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Linewraps are going to be a problem - delete all "\n" from the last few lines
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You don't want to remove \n just remove the wraps.
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BCM61B does not have two independent transistors.
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So you probably want BCM847BS which has two independent matched transistors and a very low price at digikey, so may as well
use
two
of them as shown below.
>
I took the model from
https://github.com/peteut/spice-models/blob/master/nxp/complex_discretes/complex_discretes.txt
>
It should only be necessary to unwrap the last line of the following.
Don't remove \n just remove the wraps, you may need to use a horizontal scroll bar.
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Version 4.1
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Best to just offset the integrator output so the amplitude is brought
under control sooner.
>
>
Wow. That has much lower distortion too.
>
If you just replace Q1,2 duals with a simple long tailed pair I think
you will get better performance.
>
I've reworked my version of the circuit to incorporate most of John May's changes. I really dislike the Zener diode at D3 and have
solved that particular problem in a different way. My updated version has a 4kHz spike at 150dB below the fundamental and all the
other harmonics are even lower.
>
I'm inclined to agree with the proposition that two dual transistors is an over-kill, but my attempts at getting a long-tailed
pair solution to work didn't get anywhere. I need to rip up a few more ill-founded schemes.
>
Are you sure that's the correct circuit?
It looks very similar to a circuit you posted yesterday and LTSpice 24.1.5 says 125dB down at 4 KHz.
Low distortion sinewave oscillator without big capacitor.
Re: Low distortion sinewave oscillator without big capacitor.