Re: The low distortion oscillator problem

On Thu, 6 Feb 2025 16:47:10 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:

On 6/02/2025 4:08 pm, JM wrote:

On Thu, 6 Feb 2025 03:58:59 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
 

There have been quite a few postings about 1kHz low distortion sine wave
oscillators.
>
The problem is that if you want a get stable output from a sine wave
oscillator you have to add a non-linear element to control the gain
around the oscillating circuit.
>

 
You don't'

>
Counter-example?
>
Clipping is a non-linear process. The most linear op amp becomes
non-linear as soon as its output hits the supply rails.
>
<snip>

Version 4
SHEET 1 3020 1316
WIRE 208 -192 -160 -192
WIRE 928 -192 288 -192
WIRE -160 -80 -160 -192
WIRE 208 -80 -160 -80
WIRE 528 -80 288 -80
WIRE -160 32 -160 -80
WIRE -48 32 -160 32
WIRE 96 32 32 32
WIRE 208 32 96 32
WIRE 336 32 288 32
WIRE 384 32 336 32
WIRE 528 32 528 -80
WIRE 528 32 448 32
WIRE 608 32 528 32
WIRE 736 32 688 32
WIRE 784 32 736 32
WIRE 928 32 928 -192
WIRE 928 32 848 32
WIRE -160 144 -160 32
WIRE -48 144 -160 144
WIRE 336 144 336 32
WIRE 384 144 336 144
WIRE 736 144 736 32
WIRE 784 144 736 144
WIRE -336 160 -336 144
WIRE -336 160 -400 160
WIRE 96 160 96 32
WIRE 96 160 16 160
WIRE 528 160 528 32
WIRE 528 160 448 160
WIRE 928 160 928 32
WIRE 928 160 848 160
WIRE 1216 160 928 160
WIRE -400 176 -400 160
WIRE -336 176 -336 160
WIRE -48 176 -160 176
WIRE 384 176 336 176
WIRE 784 176 736 176
WIRE 336 208 336 176
WIRE 736 208 736 176
WIRE -160 288 -160 176
WIRE -64 288 -160 288
WIRE 528 288 528 160
WIRE 528 288 16 288
WIRE 1264 288 528 288
WIRE -160 368 -160 288
WIRE 272 400 192 400
WIRE 416 400 336 400
WIRE 928 448 928 160
WIRE 928 448 848 448
WIRE 192 496 192 400
WIRE 272 496 192 496
WIRE 416 496 416 400
WIRE 416 496 336 496
WIRE 544 496 496 496
WIRE 672 496 624 496
WIRE 1040 512 848 512
WIRE 1120 512 1040 512
WIRE 1216 512 1120 512
WIRE 1040 560 1040 512
WIRE 1216 560 1216 512
WIRE 1120 576 1120 512
WIRE 1264 576 1264 288
WIRE 192 592 192 496
WIRE 240 592 192 592
WIRE 320 592 304 592
WIRE 416 592 416 496
WIRE 416 592 400 592
WIRE -208 640 -240 640
WIRE -160 640 -160 448
WIRE -160 640 -208 640
WIRE 1216 656 1216 640
WIRE 1264 656 1264 624
WIRE 1264 656 1216 656
WIRE 192 672 192 592
WIRE -240 688 -240 640
WIRE -160 688 -160 640
WIRE 1040 688 1040 640
WIRE 1120 688 1120 640
WIRE 1216 688 1216 656
WIRE 416 704 416 592
WIRE 416 704 336 704
WIRE 496 704 496 496
WIRE 496 704 416 704
WIRE 544 704 496 704
WIRE 672 704 624 704
WIRE 928 704 736 704
WIRE -16 720 -48 720
WIRE 32 720 -16 720
WIRE 192 720 192 672
WIRE 192 720 112 720
WIRE 272 720 192 720
WIRE 416 736 336 736
WIRE -16 768 -16 720
WIRE 416 768 416 736
WIRE 928 768 928 704
WIRE -240 816 -240 768
WIRE -208 816 -240 816
WIRE -160 816 -160 768
WIRE -160 816 -208 816
WIRE -160 864 -160 816
WIRE -16 864 -16 832
FLAG 336 208 0
FLAG 736 208 0
FLAG -400 176 0
FLAG -336 64 vcc
FLAG -336 256 vee
FLAG 1216 160 vout
FLAG 192 672 vx
FLAG -208 640 vt
FLAG -208 816 vb
FLAG -160 864 0
FLAG -16 864 0
FLAG 1216 688 0
FLAG 1120 688 0
FLAG 1040 688 0
FLAG 416 768 0
FLAG 928 848 0
FLAG -16 128 vcc
FLAG -16 192 vee
FLAG 416 128 vcc
FLAG 416 192 vee
FLAG 816 128 vcc
FLAG 816 192 vee
FLAG 304 688 vcc
FLAG 304 752 vee
FLAG -48 720 vg
FLAG 928 704 vc
SYMBOL res 48 16 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 10K
SYMBOL res 304 16 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 16K
SYMBOL res 704 16 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 16K
SYMBOL cap 448 16 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL cap 848 16 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL res 304 -208 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 10K
SYMBOL res 304 -96 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R5
SYMATTR Value 800k
SYMBOL res 32 272 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R6
SYMATTR Value 30k
SYMBOL res -176 352 R0
SYMATTR InstName R7
SYMATTR Value 100
SYMBOL voltage -336 48 R0
SYMATTR InstName V1
SYMATTR Value 15
SYMBOL voltage -336 160 R0
SYMATTR InstName V2
SYMATTR Value 15
SYMBOL cap 336 480 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C3
SYMATTR Value 1u
SYMBOL res 528 720 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R10
SYMATTR Value 47k
SYMBOL cap 304 576 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C4
SYMATTR Value 10u
SYMBOL res 416 576 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R12
SYMATTR Value 22k
SYMBOL res -224 672 M0
SYMATTR InstName R8
SYMATTR Value 10Meg
SYMBOL res 640 480 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R13
SYMATTR Value 47k
SYMBOL res 128 704 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R11
SYMATTR Value 1k
SYMBOL g 1216 544 M0
WINDOW 3 -255 133 Left 2
SYMATTR Value table{-2m,0,2m,1}
SYMATTR InstName G1
SYMBOL cap 1136 576 M0
SYMATTR InstName C7
SYMATTR Value 2p
SYMBOL res 1056 544 M0
SYMATTR InstName R14
SYMATTR Value 1
SYMBOL SpecialFunctions\sample 768 480 M0
SYMATTR InstName A1
SYMBOL cap -32 768 R0
SYMATTR InstName C8
SYMATTR Value 10u
SYMBOL voltage 928 752 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V4
SYMATTR Value PWL(0 0 3 -6)
SYMBOL OpAmps\LT1679 -16 160 R0
SYMATTR InstName U1
SYMBOL OpAmps\LT1679 416 160 R0
SYMATTR InstName U2
SYMBOL OpAmps\LT1679 816 160 R0
SYMATTR InstName U3
SYMBOL OpAmps\LT1679 304 720 M0
SYMATTR InstName U4
SYMBOL bi -160 688 R0
WINDOW 3 -236 218 Left 2
SYMATTR Value I={v(vt,vb)/(-100*limit(-1m,v(vg)-0.7,-15))}
SYMATTR InstName B1
SYMBOL diode 672 720 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL diode 272 416 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D2
SYMATTR Value 1N914
TEXT 1048 -104 Left 2 !.tran 0 5 0 1u startup
TEXT 1048 -128 Left 2 !.options plotwinsize=0 numdgt=15
TEXT 1056 -80 Left 2 !.save v(vout) v(vg) v(vc)