Sujet : Re: Final final 1kHz oscillator
De : bill.sloman (at) *nospam* ieee.org (Bill Sloman)
Groupes : sci.electronics.designDate : 20. Nov 2024, 03:29:37
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <vhjhin$24eu4$2@dont-email.me>
References : 1 2 3 4 5 6 7
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On 20/11/2024 12:59 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vhibce$1t7v2$1@dont-email.me...
On 18/11/2024 2:58 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:n7iijjdeqecl0kmub0bq5in0dbm60m7qam@4ax.com...
On Thu, 14 Nov 2024 11:14:28 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:t5fajjdteskfftvkf84iqsp2vc4b9ta5kj@4ax.com...
On Fri, 8 Nov 2024 15:43:41 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
I've taken John May seriously, and reworked my phase shift oscillator to use three op amps, all with their non-inverting inputs
tied to ground.
>
The results aren't all that impressive, the lower harmonics are about 65dB below the fundamental. Start-up is slow - it takes
about five seconds of simulation before the circuit settles down into steady state operation, and that after I dropped the
integrating capacitor from 6.8uF to 680nF. The nice thing about the circuit is that I can explain what each bit is doing. I can
see a few tweaks that might be worth trying.
>
The simulation died after 3 seconds, as if insufficient gain to sustain oscillation.
The circuit starts off by reducing gain. I think I can do something about that.
You seem to have a lot of components.
But I know what they all do.
Are you sure you really need all those ferrites?
No, but they are cheap, and op amps injecting hash into the power rails are never a good idea. Power supply rejection drops with frequency, and U1 in particular pulls spikes of current from the power rails twice per cycle.
Here's my really definitely final final offering.
A comfortable 90dB down at 2kHz and > 100 dB elsewhere.
Also looks clean either side of 1kHz.
Whether or not this has anything to do with reality I do not know.
The diode stabilizer string will be temperature dependent,
requiring readjustment of R4 and a total of three adjustments are needed.
Only three op amps (two packages) are needed.
I'll take a look at it.
-- Bill Sloman, Sydney
Final final 1kHz oscillator
Re: Final final 1kHz oscillator