Re: Random thoughts on sinewave oscillators

On 17/10/2024 12:32 pm, piglet wrote:

On 16/10/2024 9:55 pm, Edward Rawde wrote:

Is the reason why this doesn't produce a better looking sinewave because the amplifier slew rate is faster going down than it is
going up or some other reason?
>
Ignore the wild decoupling, it took me long enough to get the concept to work at all.
>
I'm aware that a single package containing two op amps could probably do a much better job.
>
Open the file in notepad++ (which you do use don't you?) and under encoding select Convert to ANSI. Save the file.
That will fix issues with u symbols.
>
Version 4
SHEET 1 2772 1280
WIRE 112 -144 -304 -144
WIRE 352 -144 112 -144
WIRE 640 -144 352 -144
WIRE 1456 -144 640 -144
WIRE 1728 -144 1456 -144
WIRE 2064 -144 1728 -144
WIRE 352 -128 352 -144
WIRE 112 -112 112 -144
WIRE 640 -112 640 -144
WIRE 2064 -96 2064 -144
WIRE 1728 -80 1728 -144
WIRE 1456 -64 1456 -144
WIRE 352 -16 352 -48
WIRE 352 -16 256 -16
WIRE 112 0 112 -32
WIRE 112 0 0 0
WIRE 352 0 352 -16
WIRE 640 16 640 -32
WIRE 768 16 640 16
WIRE 2064 16 2064 -16
WIRE 2176 16 2064 16
WIRE 112 32 112 0
WIRE 256 32 256 -16
WIRE 1728 32 1728 0
WIRE 1728 32 1632 32
WIRE 1888 32 1728 32
WIRE 0 48 0 0
WIRE 768 64 768 16
WIRE 1456 64 1456 16
WIRE 1456 64 1360 64
WIRE 2176 64 2176 16
WIRE 640 80 640 16
WIRE 1632 80 1632 32
WIRE 1888 80 1888 32
WIRE 352 128 352 80
WIRE 576 128 352 128
WIRE 1456 128 1456 64
WIRE 1568 128 1456 128
WIRE 1984 128 1952 128
WIRE 2064 128 2064 16
WIRE 256 144 256 96
WIRE 0 160 0 112
WIRE 112 160 112 112
WIRE 208 160 112 160
WIRE 768 176 768 128
WIRE 1360 176 1360 64
WIRE 1456 176 1456 128
WIRE 2176 176 2176 128
WIRE 112 192 112 160
WIRE 208 192 208 160
WIRE 400 208 256 208
WIRE 640 208 640 176
WIRE 640 208 464 208
WIRE -304 256 -304 -144
WIRE 352 256 352 128
WIRE 112 304 112 272
WIRE 256 304 256 208
WIRE 256 304 112 304
WIRE 288 304 256 304
WIRE 640 320 640 208
WIRE 704 320 640 320
WIRE 880 320 784 320
WIRE 1024 320 944 320
WIRE 1056 320 1024 320
WIRE 1168 320 1120 320
WIRE 1296 320 1248 320
WIRE 1360 320 1360 240
WIRE 1360 320 1296 320
WIRE 1456 320 1456 256
WIRE 1456 320 1360 320
WIRE 1984 320 1984 128
WIRE 2064 320 2064 208
WIRE 2064 320 1984 320
WIRE 112 352 112 304
WIRE 1888 352 1888 176
WIRE 1888 352 1744 352
WIRE 208 384 208 256
WIRE 352 384 352 352
WIRE 352 384 208 384
WIRE -32 400 -144 400
WIRE 32 400 -32 400
WIRE 48 400 32 400
WIRE 352 400 352 384
WIRE 2064 432 2064 320
WIRE 2192 432 2064 432
WIRE -144 448 -144 400
WIRE 640 480 640 320
WIRE 656 480 640 480
WIRE 736 480 720 480
WIRE 848 480 816 480
WIRE 960 480 848 480
WIRE 112 496 112 448
WIRE 144 496 112 496
WIRE 448 496 144 496
WIRE 544 496 512 496
WIRE 640 496 640 480
WIRE 640 496 624 496
WIRE -32 512 -32 400
WIRE 16 512 -32 512
WIRE 112 512 112 496
WIRE 112 512 80 512
WIRE -32 528 -32 512
WIRE 112 528 112 512
WIRE 208 528 112 528
WIRE 352 528 352 480
WIRE 432 528 352 528
WIRE 2064 528 2064 432
WIRE 112 544 112 528
WIRE 352 544 352 528
WIRE 1632 544 1632 176
WIRE 1632 544 1536 544
WIRE 2192 544 2192 432
WIRE 1024 560 1024 320
WIRE 1456 560 1456 320
WIRE 640 576 640 496
WIRE 640 576 544 576
WIRE 272 592 256 592
WIRE 1632 592 1632 544
WIRE 1888 592 1888 352
WIRE 640 608 640 576
WIRE 848 608 848 480
WIRE 112 640 112 624
WIRE 208 640 208 624
WIRE 208 640 112 640
WIRE -32 656 -32 608
WIRE 352 656 352 624
WIRE 352 656 -32 656
WIRE 112 688 112 640
WIRE 112 688 -32 688
WIRE -32 720 -32 688
WIRE 112 720 112 688
WIRE 352 720 352 656
WIRE 432 720 432 528
WIRE -304 832 -304 336
WIRE -32 832 -32 784
WIRE -32 832 -304 832
WIRE -16 832 -32 832
WIRE 96 832 -16 832
WIRE 112 832 112 800
WIRE 112 832 96 832
WIRE 352 832 352 800
WIRE 352 832 112 832
WIRE 432 832 432 784
WIRE 432 832 352 832
WIRE 640 832 640 688
WIRE 640 832 432 832
WIRE 848 832 848 688
WIRE 848 832 640 832
WIRE 1024 832 1024 624
WIRE 1024 832 848 832
WIRE 1456 832 1456 624
WIRE 1456 832 1024 832
WIRE 1632 832 1632 672
WIRE 1632 832 1456 832
WIRE 1888 832 1888 672
WIRE 1888 832 1632 832
WIRE 2064 832 2064 608
WIRE 2064 832 1888 832
WIRE 2192 832 2192 608
WIRE 2192 832 2064 832
WIRE -304 864 -304 832
WIRE -16 880 -16 832
WIRE 96 896 96 832
WIRE 272 896 272 592
WIRE 1408 896 272 896
WIRE 1536 896 1536 544
WIRE 1536 896 1408 896
WIRE -144 1008 -144 512
WIRE -16 1008 -16 960
WIRE -16 1008 -144 1008
WIRE 96 1008 96 960
WIRE 96 1008 -16 1008
WIRE 208 1008 96 1008
WIRE 320 1008 272 1008
WIRE 544 1008 544 576
WIRE 544 1008 400 1008
WIRE 960 1008 960 480
WIRE 1104 1008 960 1008
WIRE 1232 1008 1104 1008
FLAG 768 176 0
FLAG 1104 1008 2khz-sine-out
FLAG -304 864 0
FLAG 0 160 0
FLAG 256 144 0
FLAG 32 400 In+
FLAG 144 496 In-
FLAG 2176 176 0
FLAG 1408 896 amplitude-control
FLAG 1296 320 vdet
DATAFLAG 592 208 "round(($)*100)/100"
DATAFLAG 400 528 "round(($)*100)/100"
DATAFLAG 160 640 "round(($)*100)/100"
DATAFLAG -80 400 "round(($)*100)/100"
DATAFLAG 224 496 "round(($)*100)/100"
DATAFLAG 64 688 "round(($)*100)/100"
DATAFLAG 160 160 "round(($)*100)/100"
DATAFLAG 160 304 "round(($)*100)/100"
DATAFLAG 256 384 "round(($)*100)/100"
DATAFLAG 400 128 "round(($)*100)/100"
DATAFLAG -192 -144 "round(($)*100)/100"
DATAFLAG 688 16 "round(($)*100)/100"
DATAFLAG 1520 128 "round(($)*100)/100"
DATAFLAG 2128 432 "round(($)*100)/100"
DATAFLAG 1824 352 "round(($)*100)/100"
DATAFLAG 1584 544 "round(($)*100)/100"
DATAFLAG 1408 320 "round(($)*100)/100"
DATAFLAG 1824 32 "round(($)*100)/100"
SYMBOL res 96 -128 R0
WINDOW 3 36 73 Left 2
SYMATTR Value 15k
SYMATTR InstName R1
SYMBOL voltage -304 240 R0
WINDOW 123 0 0 Left 0
WINDOW 39 -151 71 Left 2
WINDOW 3 -79 36 Left 2
SYMATTR SpiceLine Rser=0.1
SYMATTR Value 12
SYMATTR InstName V1
SYMBOL npn 48 352 R0
SYMATTR InstName Q1
SYMATTR Value BC847C
SYMBOL res 96 176 R0
WINDOW 0 -46 26 Left 2
WINDOW 3 -68 68 Left 2
SYMATTR InstName R2
SYMATTR Value 150k
SYMBOL npn 576 80 R0
SYMATTR InstName Q3
SYMATTR Value BC847C
SYMBOL res 336 -144 R0
WINDOW 3 35 73 Left 2
SYMATTR Value 1k
SYMATTR InstName R3
SYMBOL npn 288 256 R0
SYMATTR InstName Q2
SYMATTR Value BC847C
SYMBOL res 96 528 R0
WINDOW 3 -47 71 Left 2
WINDOW 0 -37 45 Left 2
SYMATTR Value 470
SYMATTR InstName R4
SYMBOL res 96 704 R0
WINDOW 3 37 67 Left 2
SYMATTR Value 39k
SYMATTR InstName R5
SYMBOL res -48 512 R0
WINDOW 0 -41 40 Left 2
WINDOW 3 -66 68 Left 2
SYMATTR InstName R6
SYMATTR Value 270k
SYMBOL cap 80 496 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 470p
SYMBOL polcap -48 720 R0
SYMATTR InstName C3
SYMATTR Value 220ľ
SYMBOL cap 464 192 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C5
SYMATTR Value 10p
SYMBOL res 336 528 R0
WINDOW 0 35 32 Left 2
WINDOW 3 37 62 Left 2
SYMATTR InstName R10
SYMATTR Value 5.6k
SYMBOL res 336 704 R0
WINDOW 0 -53 28 Left 2
WINDOW 3 -50 58 Left 2
SYMATTR InstName R11
SYMATTR Value 10k
SYMBOL res 336 384 R0
WINDOW 0 -59 43 Left 2
WINDOW 3 -59 70 Left 2
SYMATTR InstName R12
SYMATTR Value 2.2k
SYMBOL res -32 864 R0
SYMATTR InstName R15
SYMATTR Value 470k
SYMBOL cap 80 896 R0
SYMATTR InstName C6
SYMATTR Value 270pf
SYMBOL cap 208 1024 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C7
SYMATTR Value 270pf
SYMBOL polcap -160 448 R0
SYMATTR InstName C8
SYMATTR Value 1ľ
SYMBOL polcap 416 720 R0
SYMATTR InstName C9
SYMATTR Value 100ľ
SYMBOL polcap 752 64 R0
SYMATTR InstName C10
SYMATTR Value 220ľ
SYMBOL polcap 656 496 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C11
SYMATTR Value 1ľ
SYMBOL res 832 464 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R16
SYMATTR Value 100
SYMBOL res 832 592 R0
SYMATTR InstName R17
SYMATTR Value 1Meg
SYMBOL res 96 16 R0
WINDOW 3 36 73 Left 2
SYMATTR Value 33k
SYMATTR InstName R18
SYMBOL polcap -16 48 R0
SYMATTR InstName C12
SYMATTR Value 22ľ
SYMBOL polcap 192 192 R0
WINDOW 0 -40 9 Left 2
WINDOW 3 -47 54 Left 2
SYMATTR InstName C2
SYMATTR Value 22ľ
SYMBOL res 336 -16 R0
WINDOW 3 35 73 Left 2
SYMATTR Value 22k
SYMATTR InstName R19
SYMBOL polcap 240 32 R0
SYMATTR InstName C13
SYMATTR Value 22ľ
SYMBOL res 304 1024 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R8
SYMATTR Value 470k
SYMBOL polcap 512 480 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C4
SYMATTR Value 10ľ
SYMBOL res 624 592 R0
SYMATTR InstName R7
SYMATTR Value 3.3k
SYMBOL res 640 480 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R13
SYMATTR Value 1.5k
SYMBOL pjf 256 528 M0
WINDOW 0 -24 6 Left 2
WINDOW 3 -49 37 Left 2
SYMATTR InstName J1
SYMATTR Value J175
SYMBOL res 624 -128 R0
SYMATTR InstName R20
SYMATTR Value 470
SYMBOL res 800 304 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R22
SYMATTR Value 100
SYMBOL cap 944 304 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C16
SYMATTR Value 0.1ľ
SYMBOL diode 1008 560 R0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode 1120 304 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL cap 1440 560 R0
SYMATTR InstName C17
SYMATTR Value 10ľ
SYMBOL res 1440 160 R0
SYMATTR InstName R23
SYMATTR Value 220k
SYMBOL res 1264 304 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R24
SYMATTR Value 22k
SYMBOL pnp 1568 176 M180
SYMATTR InstName Q4
SYMATTR Value BC857C
SYMBOL res 1712 -96 R0
SYMATTR InstName R25
SYMATTR Value 10k
SYMBOL pnp 1952 176 R180
SYMATTR InstName Q5
SYMATTR Value BC857C
SYMBOL res 2048 112 R0
SYMATTR InstName R26
SYMATTR Value 22k
SYMBOL res 2048 512 R0
SYMATTR InstName R27
SYMATTR Value 22k
SYMBOL res 2048 -112 R0
SYMATTR InstName R28
SYMATTR Value 22k
SYMBOL polcap 2160 64 R0
SYMATTR InstName C18
SYMATTR Value 220ľ
SYMBOL res 1616 576 R0
SYMATTR InstName R29
SYMATTR Value 22k
SYMBOL res 1872 576 R0
SYMATTR InstName R30
SYMATTR Value 22k
SYMBOL cap 2176 544 R0
SYMATTR InstName C19
SYMATTR Value 1ľ
SYMBOL res 1440 -80 R0
SYMATTR InstName R31
SYMATTR Value 220k
SYMBOL cap 1376 240 R180
WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2
SYMATTR InstName C21
SYMATTR Value 10ľ
TEXT -424 800 Left 2 !.tran 100
TEXT 632 -200 Left 3 ;Edward Rawde's weird sinewave oscillator. October 2024
>
>

 I assume this is an intellectual challenge and not a real project? I suspect the jfet gate-channel is forward biased so the amplitude control section is my first place to look?
 piglet
 

Hmm, that forward biased gate only happens during startup. Some other ideas:
The amp input bias R6 loads the Wien network too much - try lowering the Wien network impedance?
Replace R7 with constant current sink if you think slew rate is the issue?
Rectifier load is too heavy on the follower - increase R22?
Q5 base reference is not stiff enough - lower R26-27-28?
Q4 base current flows through rectifier - reference D1 instead to +12 rail?
Maybe later I will find time to explore...
piglet