Re: Final final 1kHz oscillator

"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.

You seem to have a lot of components.
Are you sure you really need all those ferrites?

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.

Version 4
SHEET 1 2196 932
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WIRE 48 -672 0 -672
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FLAG -480 400 0
FLAG 288 528 V+
FLAG 144 224 V-
FLAG -320 160 V+
FLAG -320 656 V-
FLAG 880 288 output
FLAG 144 32 V+
FLAG 288 624 V-
FLAG 432 768 0
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FLAG -32 -384 V-
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FLAG 192 576 dc-trim
FLAG 640 -512 0
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SYMBOL cap -272 224 R0
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WINDOW 3 -79 48 Left 2
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SYMATTR Value 10000n
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SYMBOL cap -272 496 R0
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WINDOW 3 -75 50 Left 2
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SYMATTR Value 10000n
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SYMBOL cap -16 224 R180
WINDOW 0 23 78 Left 2
WINDOW 3 -74 78 Left 2
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SYMATTR Value 10000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL diode -80 688 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
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SYMATTR Value 1N4148
SYMBOL cap -64 688 M180
WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2
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SYMATTR Value 1000n
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SYMBOL OpAmps\LT1678 -32 -432 M0
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WINDOW 3 -47 89 Left 2
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SYMBOL diode 192 -544 R90
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WINDOW 3 32 32 VTop 2
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SYMATTR Value 1N4148
SYMBOL diode 272 -544 R90
WINDOW 0 58 31 VBottom 2
WINDOW 3 -28 34 VTop 2
SYMATTR InstName D7
SYMATTR Value 1N4148
SYMBOL diode 352 -544 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D8
SYMATTR Value 1N4148
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WINDOW 3 -27 31 VTop 2
SYMATTR InstName D9
SYMATTR Value 1N4148
SYMBOL diode 512 -544 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D10
SYMATTR Value 1N4148
SYMBOL schottky 608 -288 R0
WINDOW 3 -16 -25 VRight 2
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SYMATTR InstName D2
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res -80 -560 R270
WINDOW 0 33 55 VTop 2
WINDOW 3 -3 55 VBottom 2
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SYMATTR Value 3.3k
SYMBOL res 32 -384 R0
SYMATTR InstName R6
SYMATTR Value 10k
SYMBOL diode 592 -544 R90
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WINDOW 3 -25 30 VTop 2
SYMATTR InstName D11
SYMATTR Value 1N4148
SYMBOL res 912 304 R0
SYMATTR InstName R19
SYMATTR Value 600
SYMBOL OpAmps\LT1678 288 576 M0
WINDOW 0 23 -47 Left 2
WINDOW 3 19 37 Left 2
SYMATTR InstName U2B
SYMBOL cap 0 -688 R90
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WINDOW 3 32 32 VTop 2
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SYMATTR Value 47p
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WINDOW 0 0 56 VBottom 2
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SYMATTR InstName R20
SYMATTR Value 470k
TEXT -496 696 Left 2 !.tran 0 350s 50s startup
TEXT 72 -664 Left 2 ;R4 18k ten turn.
TEXT 72 -640 Left 2 ;Adjust for correct gate voltage,
TEXT 72 -616 Left 2 ;minimum distortion and good
TEXT 72 -592 Left 2 ;settling time at power on.
TEXT -328 40 Left 2 ;R3 150 ohm ten turn.
TEXT -328 72 Left 2 ;Adjust for minimum distortion.
TEXT 296 48 Left 2 ;R9 1Meg ten turn.
TEXT 952 272 Left 2 ;1kHz, > 90dB harmonic purity
TEXT 744 504 Left 2 ;Copyright Edward Rawde, Nov 2024.
TEXT 744 536 Left 2 ;rawde dot edward at the popular email
TEXT 744 472 Left 2 ;Not for commercial use.
TEXT -448 -640 Left 2 ;1kHz sinewave oscillator,
TEXT -448 -616 Left 2 ;> 90dB harmonic purity.
TEXT 744 568 Left 2 ;service everyone uses for some reason.