Final final 1kHz oscillator

This is the simplest circuit I can come up with.
Harmonics are more than 80dB down in simulation.
FFT the last 30 seconds.
There is only one harmonic stopping me claiming 90dB but the exact FFT result can depend
on exactly how much output is selected for the FFT. You may see different results.

If a prototype is ever built, attention to the type and quality of the capacitors used will be needed.
Electrolytics are not intended. Put C1 and C2 near U1 supply pins.
Also pay attention to the stability of +/- 6V.
It would be nice to have a single 12V rail version but so far I can't get it to work.

R1 and R2 and probably R7 should be easily changeable.
R3 should be 220 ohm ten turn. R9 should be 1M ohm ten turn in series with 470k.

I don't fully understand why the DC stabilization circuit through U2B achieves what it does
and this makes me concerned about whether a real circuit would have the same behaviour.
It was added when I noticed that the diodes D1 and D2 weren't contributing equally so I
decided to try to derive a DC correction signal. This was originally connected to the FET source
and then to R13. Since this is a DC correction signal I decided to try out the effect of
connecting it to U1 Vocm and was amazed that this works as well as it does.
If you disconnect R5, harmonics will not be more than 50dB down because D1 and D2 are no
longer providing stable and equal contributions to the level control feedback.

If you need even better performance then the circuit referenced by Bill Sloman can be used.
https://www.google.com/search?q=AN132+purity
NSL-32SR3 is not expensive and simulation models exist but LT1468 is expensive.

Other references

https://www.google.com/search?&q=The+field+effect+transistor+as+a+voltage+controlled+resistor

https://www.google.com/search?&q=sine+wave+oscillator&udm=2


Version 4
SHEET 1 2196 932
WIRE -64 -672 -96 -672
WIRE 48 -672 0 -672
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FLAG -400 336 0
FLAG 288 560 V+
FLAG 144 224 V-
FLAG -240 96 V+
FLAG -240 592 V-
FLAG 768 144 output
FLAG 144 32 V+
FLAG 288 656 V-
FLAG 432 800 0
FLAG 16 256 0
FLAG -32 -480 V+
FLAG -32 -384 V-
FLAG -256 0 0
FLAG 400 -240 0
FLAG 160 -240 0
FLAG 848 416 0
FLAG 64 416 0
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FLAG -48 800 0
FLAG 208 608 dc-trim
SYMBOL voltage -320 128 R0
WINDOW 123 0 0 Left 0
WINDOW 39 10 135 Left 2
WINDOW 0 12 7 Left 2
WINDOW 3 15 104 Left 2
SYMATTR SpiceLine Rser=0.01
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SYMATTR Value 6
SYMBOL res 496 256 R90
WINDOW 0 1 52 VBottom 2
WINDOW 3 33 45 VTop 2
SYMATTR InstName R11
SYMATTR Value 10.5k
SYMBOL cap 352 256 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 35 30 VTop 2
SYMATTR InstName C8
SYMATTR Value 0.015�
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WINDOW 3 35 56 VTop 2
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SYMBOL res 448 -144 R90
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WINDOW 3 39 55 VTop 2
SYMATTR InstName R8
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SYMBOL njf -128 -176 R90
WINDOW 0 -37 23 VRight 2
WINDOW 3 -9 -3 VRight 2
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WINDOW 39 10 135 Left 2
WINDOW 0 10 0 Left 2
WINDOW 3 15 104 Left 2
SYMATTR SpiceLine Rser=0.01
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SYMBOL res 48 272 R0
WINDOW 3 36 65 Left 2
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SYMATTR InstName R10
SYMBOL schottky 496 -288 R0
WINDOW 3 -17 -26 VRight 2
SYMATTR Value BAS40HY
SYMATTR InstName D1
SYMATTR Description Diode
SYMATTR Type diode
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WINDOW 3 -15 -25 VRight 2
SYMATTR Value BAS40HY
SYMATTR InstName D2
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res -112 -64 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 82
SYMBOL OpAmps\LT1994 176 128 R0
WINDOW 3 10 -65 Left 2
WINDOW 0 11 -95 Left 2
SYMATTR InstName U1
SYMBOL OpAmps\LT1057 288 544 M0
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WINDOW 3 18 130 Left 2
SYMATTR InstName U2B
SYMBOL schottky 528 480 M0
WINDOW 3 52 -26 VRight 2
WINDOW 0 -18 3 Left 2
SYMATTR Value BAS40HY
SYMATTR InstName D3
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL schottky 640 480 M0
WINDOW 3 49 -26 VRight 2
WINDOW 0 -21 4 Left 2
SYMATTR Value BAS40HY
SYMATTR InstName D4
SYMATTR Description Diode
SYMATTR Type diode
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WINDOW 3 25 87 Left 2
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SYMBOL res 720 640 M0
WINDOW 3 27 87 Left 2
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SYMATTR InstName R17
SYMBOL res -112 -256 R0
WINDOW 0 38 42 Left 2
WINDOW 3 36 66 Left 2
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SYMBOL res 320 -384 R0
WINDOW 0 -55 41 Left 2
WINDOW 3 -64 83 Left 2
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SYMBOL res 448 -32 R90
WINDOW 0 -4 61 VBottom 2
WINDOW 3 39 55 VTop 2
SYMATTR InstName R9
SYMATTR Value 1.0469Meg
SYMBOL res -80 -288 R180
WINDOW 0 40 70 Left 2
WINDOW 3 45 42 Left 2
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res -32 432 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
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SYMATTR Value 33k
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WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R15
SYMATTR Value 220
SYMBOL res 16 592 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R14
SYMATTR Value 10k
SYMBOL cap 176 352 R180
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WINDOW 3 -88 16 Left 2
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SYMATTR Value 0.015�
SYMATTR SpiceLine V=16 Irms=271m Rser=0.594318 Lser=0 mfg="KEMET" pn="C0603C153K4RAC" type="X7R"
SYMBOL OpAmps\LT1057 -32 -496 M0
WINDOW 0 -63 128 Left 2
WINDOW 3 -54 156 Left 2
SYMATTR InstName U2A
SYMBOL cap 720 128 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C13
SYMATTR Value 1�
SYMATTR SpiceLine V=10 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM153R61A105ME95" type="X5R"
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SYMATTR Value 100k
SYMBOL res 32 -384 R0
SYMATTR InstName R6
SYMATTR Value 22k
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WINDOW 3 -6 55 VBottom 2
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SYMBOL res -80 -560 R270
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WINDOW 3 -3 56 VBottom 2
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SYMATTR Value 47k
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WINDOW 3 -31 54 Left 2
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SYMATTR Value 10�
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SYMBOL cap 416 -352 M0
WINDOW 0 -36 9 Left 2
WINDOW 3 -31 54 Left 2
SYMATTR InstName C10
SYMATTR Value 10�
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap 368 496 M270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C9
SYMATTR Value 10�
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap 416 672 R0
WINDOW 0 -37 6 Left 2
WINDOW 3 -31 54 Left 2
SYMATTR InstName C11
SYMATTR Value 10�
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap 608 672 R0
WINDOW 0 -33 9 Left 2
WINDOW 3 -31 54 Left 2
SYMATTR InstName C12
SYMATTR Value 10�
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap -192 160 R0
WINDOW 0 -22 9 Left 2
WINDOW 3 -31 54 Left 2
SYMATTR InstName C1
SYMATTR Value 10�
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap -192 432 R0
WINDOW 0 -22 9 Left 2
WINDOW 3 -31 54 Left 2
SYMATTR InstName C2
SYMATTR Value 10�
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap 32 224 R180
WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2
SYMATTR InstName C4
SYMATTR Value 10�
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL diode -32 720 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D5
SYMATTR Value 1N4148
SYMBOL cap 0 -688 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C3
SYMATTR Value 10�
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap -16 720 M180
WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2
SYMATTR InstName C5
SYMATTR Value 1�
SYMATTR SpiceLine V=10 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM153R61A105ME95" type="X5R"
TEXT -624 272 Left 2 !.tran 0 300s 0s startup
TEXT -1568 -728 Left 2 ;Edward Rawde's high purity 1kHz sinewave oscillator. 8 Nov 2024\n \nHarmonics are more than 80dB down in
simulation.\nFFT the last 30 seconds.\nThere is only one harmonic stopping me claiming 90dB but the exact FFT result can depend\non
exactly how much output is selected for the FFT. You may see different results.\n \nIf a prototype is ever built, pay attention to
the type and quality of the capacitors used.\nElectrolytics are not intended. Put C1 and C2 near U1 supply pins.\nAlso pay attention
to the stability of +/- 6V.\nIt would be nice to have a single 12V rail version but so far I can't get it to work.\n \nR1 and R2 and
probably R7 should be easily changeable.\nR3 should be 220 ohm ten turn. R9 should be 1M ohm ten turn in series with 470k.\n \nI
don't fully understand why the DC stabilization circuit through U2B achieves what it does\nand this makes me concerned about whether
a real circuit would have the same behaviour.\nIt was added when I noticed that the diodes D1 and D2 weren't contributing equally so
I \ndecided to try to derive a DC correction signal. This was originally connected to the FET source\nand then to R13. Since this is
a DC correction signal I decided to try out the effect of\nconnecting it to U1 Vocm and was amazed that this works as well as it
does. \nIf you disconnect R5, harmonics will not be more than 50dB down because D1 and D2 are no\nlonger providing stable and equal
contributions to the level control feedback.\n \nIf you need even better performance then the circuit referenced by Bill Sloman can
be used.\nhttps://www.google.com/search?q=AN132+purity\nNSL-32SR3 is not expensive and simulation models exist but LT1468 is
expensive.\n \nOther references\n \nhttps://www.google.com/search?&q=The+field+effect+transistor+as+a+voltage+controlled+resistor\n
\nhttps://www.google.com/search?&q=sine+wave+oscillator&udm=2