Re: Final final 1kHz oscillator

"Cursitor Doom" <cd@notformail.com> wrote in message news:ee92jjllg5kudr83e8bvvbsjba754aecjs@4ax.com...

On Sun, 10 Nov 2024 18:00:01 +0000, Cursitor Doom <cd@notformail.com>
wrote:
>

On Sun, 10 Nov 2024 17:45:00 +0000, Cursitor Doom <cd@notformail.com>
wrote:
>

On Sun, 10 Nov 2024 12:12:34 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>

"Cursitor Doom" <cd@notformail.com> wrote in message news:bs81jjt7d064jc1ktmvihgn30qkhf67taj@4ax.com...

On Sun, 10 Nov 2024 00:49:36 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vgnkgg$3p31a$1@dont-email.me...

On 9/11/2024 7:39 pm, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vgn4gm$3lcor$1@dont-email.me...

On 9/11/2024 7:43 am, Edward Rawde wrote:

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.
>

>
I have fixed my circuit but it raises more questions than it answers.
This circuit deliberately has no text and no u symbols so should be ready to simulate.
If you let it complete (about 20 minutes on a fast PC) the FFT should show at least 80dB purity and there aren't many
harmonics
standing in the way of 90dB.
Startup isn't fast and it takes at least 20 seconds of simulation to fully settle.

>
Spectral purity might be fine for all I can tell but the output
amplitude is all over the place,

>
Change R9 to 1.07Meg does it amplitude stabilize now?
Adjustment will be needed in any real circuit.

>
Indeed, but for a simulation we should be seeing identical results!
I've made the change as you suggested and it's increased the sim time
considerably. I'll post again when it's completed.

>
Update: looking *much* better at 25% done. Settled after 7.5s. I will
let it run its course anyway and post again at the end with the final
outcome.

>
Looks really stable now; 4.5V peak to peak and none of the
fluctuations of the earlier simulations. Weird how it took *so* much
longer to complete this time,  though.

An FFT on the last 10 seconds should show peformance approaching 90dB down.

I likely won't be working on this any further unless anyone else wants further discussion.

The goal was to get the purest possible sine wave at the lowest cost and in simulation I don't think I can improve on this circuit.
I'm not able to build this circuit and even if I did I don't have equipment capable of measuring distortion 90dB down.

I'd still like to know why LT1057 doesn't work in position U2. It's not like rail to rail is needed.
LT1678 works exactly as expected. LT1057 probably would in reality but not sure I'd risk it.

I'd also like to know exactly how and why U3 stabilizes U1 and the operation of D1 and D2.
Would this work the same in reality?

The diode clamp should probably be made from a single diode and another op amp with two resistors to allow the clamp level to be
easily adjusted.

If it's ever buil for real I'd make R1, R2, R7, R8 easily changeable.
I'd also make R3 220 ohm ten turn and R9 1Meg 10 turn in series with 470k.

The definitely final circuit is included below.
This has no text or titles or dates so add that yourself if you wish.

Version 4
SHEET 1 2196 932
WIRE -64 -576 -96 -576
WIRE 48 -576 16 -576
WIRE 128 -528 112 -528
WIRE 208 -528 192 -528
WIRE 288 -528 272 -528
WIRE 368 -528 352 -528
WIRE 448 -528 432 -528
WIRE 528 -528 512 -528
WIRE 640 -528 592 -528
WIRE 640 -512 640 -528
WIRE -32 -464 -32 -480
WIRE 48 -448 48 -576
WIRE 48 -448 0 -448
WIRE -96 -432 -96 -576
WIRE -64 -432 -96 -432
WIRE 112 -416 112 -528
WIRE 112 -416 0 -416
WIRE 160 -416 112 -416
WIRE 208 -416 160 -416
WIRE 336 -416 288 -416
WIRE 400 -416 336 -416
WIRE 512 -416 400 -416
WIRE 624 -416 512 -416
WIRE -96 -384 -96 -432
WIRE -32 -384 -32 -400
WIRE 48 -368 48 -448
WIRE 336 -368 336 -416
WIRE 160 -352 160 -416
WIRE 400 -352 400 -416
WIRE 512 -288 512 -416
WIRE 624 -288 624 -416
WIRE -96 -272 -96 -304
WIRE -96 -272 -192 -272
WIRE -96 -240 -96 -272
WIRE 48 -240 48 -288
WIRE 160 -240 160 -288
WIRE 336 -240 336 -288
WIRE 400 -240 400 -288
WIRE -192 -176 -192 -272
WIRE -224 -128 -256 -128
WIRE -96 -128 -96 -160
WIRE -96 -128 -128 -128
WIRE -80 -128 -96 -128
WIRE 144 -128 -80 -128
WIRE 288 -128 224 -128
WIRE 352 -128 288 -128
WIRE 512 -128 512 -224
WIRE 512 -128 432 -128
WIRE -256 -48 -256 -128
WIRE -208 -48 -256 -48
WIRE -80 -48 -80 -128
WIRE -80 -48 -128 -48
WIRE 288 -16 288 -128
WIRE 288 -16 64 -16
WIRE 352 -16 288 -16
WIRE 512 -16 512 -128
WIRE 512 -16 432 -16
WIRE -256 0 -256 -48
WIRE 144 48 144 32
WIRE -272 96 -352 96
WIRE -208 96 -272 96
WIRE 64 96 64 -16
WIRE 112 96 64 96
WIRE 512 96 512 -16
WIRE 512 96 272 96
WIRE -32 128 -96 128
WIRE 112 128 -32 128
WIRE -352 144 -352 96
WIRE 624 144 624 -224
WIRE 656 144 624 144
WIRE 752 144 720 144
WIRE -208 160 -208 96
WIRE -32 160 -32 128
WIRE 112 160 64 160
WIRE 624 160 624 144
WIRE 624 160 272 160
WIRE 752 176 752 144
WIRE 144 224 144 208
WIRE -32 256 -32 224
WIRE 64 272 64 160
WIRE 160 272 64 272
WIRE 288 272 160 272
WIRE 400 272 352 272
WIRE 512 272 512 96
WIRE 512 272 480 272
WIRE 64 288 64 272
WIRE 160 288 160 272
WIRE 752 288 752 256
WIRE 880 288 752 288
WIRE 928 288 880 288
WIRE -352 320 -352 224
WIRE -352 320 -432 320
WIRE 928 320 928 288
WIRE -432 336 -432 320
WIRE -352 336 -352 320
WIRE -208 336 -208 224
WIRE -208 336 -352 336
WIRE -96 336 -96 128
WIRE 64 384 64 368
WIRE 160 384 160 352
WIRE 160 384 64 384
WIRE -352 416 -352 336
WIRE 64 416 64 384
WIRE -208 432 -208 336
WIRE 192 432 144 432
WIRE 304 432 272 432
WIRE 384 432 368 432
WIRE 928 432 928 400
WIRE 512 448 512 272
WIRE 624 448 624 160
WIRE 288 544 288 528
WIRE 384 560 384 432
WIRE 384 560 320 560
WIRE 624 560 624 512
WIRE 624 560 384 560
WIRE -96 576 -96 416
WIRE -48 576 -96 576
WIRE 32 576 -48 576
WIRE 144 576 144 432
WIRE 144 576 112 576
WIRE 208 576 144 576
WIRE 256 576 208 576
WIRE -352 592 -352 496
WIRE -272 592 -352 592
WIRE -208 592 -208 496
WIRE -208 592 -272 592
WIRE 432 592 320 592
WIRE 512 592 512 512
WIRE 512 592 432 592
WIRE 624 592 624 560
WIRE 704 592 624 592
WIRE -96 624 -96 576
WIRE -48 624 -48 576
WIRE 288 624 288 608
WIRE 512 624 512 592
WIRE 704 624 704 592
WIRE 432 640 432 592
WIRE 624 640 624 592
WIRE -96 736 -96 688
WIRE -48 736 -48 688
WIRE -48 736 -96 736
WIRE 432 736 432 704
WIRE 512 736 512 704
WIRE 512 736 432 736
WIRE 624 736 624 704
WIRE 624 736 512 736
WIRE 704 736 704 704
WIRE 704 736 624 736
WIRE -96 768 -96 736
WIRE 432 768 432 736
FLAG -432 336 0
FLAG 288 528 V+
FLAG 144 224 V-
FLAG -272 96 V+
FLAG -272 592 V-
FLAG 880 288 output
FLAG 144 32 V+
FLAG 288 624 V-
FLAG 432 768 0
FLAG -32 256 0
FLAG -32 -480 V+
FLAG -32 -384 V-
FLAG -256 0 0
FLAG 400 -240 0
FLAG 160 -240 0
FLAG 64 416 0
FLAG 336 -240 0
FLAG -96 768 0
FLAG 208 576 dc-trim
FLAG 640 -512 0
FLAG 48 -240 0
FLAG 928 432 0
SYMBOL voltage -352 128 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
SYMATTR InstName V1
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 15n
SYMATTR SpiceLine V=16 Irms=271m Rser=0.594318 Lser=0 mfg="KEMET" pn="C0603C153K4RAC" type="X7R"
SYMBOL res 240 -144 R90
WINDOW 0 -1 46 VBottom 2
WINDOW 3 35 56 VTop 2
SYMATTR InstName R7
SYMATTR Value 6.34k
SYMBOL res 448 -144 R90
WINDOW 0 -4 61 VBottom 2
WINDOW 3 39 55 VTop 2
SYMATTR InstName R8
SYMATTR Value 13k
SYMBOL njf -128 -176 R90
WINDOW 0 -37 23 VRight 2
WINDOW 3 -9 -3 VRight 2
SYMATTR InstName J1
SYMATTR Value J112
SYMBOL voltage -352 400 R0
WINDOW 123 0 0 Left 0
WINDOW 39 10 135 Left 2
WINDOW 0 10 0 Left 2
WINDOW 3 15 104 Left 2
SYMATTR SpiceLine Rser=0.01
SYMATTR InstName V2
SYMATTR Value 6
SYMBOL res 48 272 R0
WINDOW 3 36 65 Left 2
SYMATTR Value 10.5k
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
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 288 512 M0
WINDOW 0 19 104 Left 2
WINDOW 3 18 130 Left 2
SYMATTR InstName U3
SYMBOL schottky 528 448 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 640 448 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
SYMBOL res 528 608 M0
WINDOW 3 25 87 Left 2
SYMATTR Value 220k
SYMATTR InstName R16
SYMBOL res 720 608 M0
WINDOW 3 27 87 Left 2
SYMATTR Value 220k
SYMATTR InstName R17
SYMBOL res -112 -256 R0
WINDOW 0 38 42 Left 2
WINDOW 3 36 66 Left 2
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL res 320 -384 R0
WINDOW 0 -50 69 Left 2
WINDOW 3 -54 98 Left 2
SYMATTR InstName R13
SYMATTR Value 220k
SYMBOL res 448 -32 R90
WINDOW 0 -4 61 VBottom 2
WINDOW 3 39 55 VTop 2
SYMATTR InstName R9
SYMATTR Value 1.07Meg
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 -80 432 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R5
SYMATTR Value 33k
SYMBOL res 176 416 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R15
SYMATTR Value 220
SYMBOL res 16 560 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R14
SYMATTR Value 10k
SYMBOL cap 176 352 R180
WINDOW 0 -37 41 Left 2
WINDOW 3 -50 13 Left 2
SYMATTR InstName C7
SYMATTR Value 15n
SYMATTR SpiceLine V=16 Irms=271m Rser=0.594318 Lser=0 mfg="KEMET" pn="C0603C153K4RAC" type="X7R"
SYMBOL cap 720 128 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C13
SYMATTR Value 100000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.002 Lser=0 mfg="TDK" pn="C575OX5ROJI07M" type="X5R"
SYMBOL res 736 160 R0
SYMATTR InstName R18
SYMATTR Value 600
SYMBOL res 192 -400 R270
WINDOW 0 35 55 VTop 2
WINDOW 3 -6 55 VBottom 2
SYMATTR InstName R12
SYMATTR Value 220k
SYMBOL cap 176 -352 M0
WINDOW 0 -22 9 Left 2
WINDOW 3 -75 48 Left 2
SYMATTR InstName C6
SYMATTR Value 10000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap 416 -352 M0
WINDOW 0 -32 51 Left 2
WINDOW 3 -72 7 Left 2
SYMATTR InstName C10
SYMATTR Value 10000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap 368 448 M270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C9
SYMATTR Value 10000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap 416 640 R0
WINDOW 0 -37 6 Left 2
WINDOW 3 -77 53 Left 2
SYMATTR InstName C11
SYMATTR Value 10000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap 608 640 R0
WINDOW 0 -33 9 Left 2
WINDOW 3 -72 51 Left 2
SYMATTR InstName C12
SYMATTR Value 10000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap -224 160 R0
WINDOW 0 -22 9 Left 2
WINDOW 3 -79 48 Left 2
SYMATTR InstName C1
SYMATTR Value 10000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap -224 432 R0
WINDOW 0 -22 9 Left 2
WINDOW 3 -75 50 Left 2
SYMATTR InstName C2
SYMATTR Value 10000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM155R60J106ME15" type="X5R"
SYMBOL cap -16 224 R180
WINDOW 0 23 78 Left 2
WINDOW 3 -74 78 Left 2
SYMATTR InstName C4
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
SYMATTR InstName D5
SYMATTR Value 1N4148
SYMBOL cap -64 688 M180
WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2
SYMATTR InstName C5
SYMATTR Value 1000n
SYMATTR SpiceLine V=6.3 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM032R60J105ME05" type="X5R"
SYMBOL OpAmps\LT1678 -32 -432 M0
WINDOW 0 -47 50 Left 2
WINDOW 3 -47 89 Left 2
SYMATTR InstName U2
SYMBOL diode 192 -544 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D6
SYMATTR Value 1N914
SYMBOL diode 272 -544 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D7
SYMATTR Value 1N914
SYMBOL diode 352 -544 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D8
SYMATTR Value 1N914
SYMBOL diode 432 -544 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D9
SYMATTR Value 1N914
SYMBOL diode 512 -544 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D10
SYMATTR Value 1N914
SYMBOL schottky 608 -288 R0
WINDOW 3 -16 -25 VRight 2
SYMATTR Value BAS40HY
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
SYMATTR InstName R4
SYMATTR Value 10k
SYMBOL res 32 -384 R0
SYMATTR InstName R6
SYMATTR Value 10k
SYMBOL diode 592 -544 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D11
SYMATTR Value 1N914
SYMBOL res 912 304 R0
SYMATTR InstName R19
SYMATTR Value 600
TEXT -448 632 Left 2 !.tran 0 150s 0s startup