Re: Random thoughts on sinewave oscillators

On 20/10/2024 4:52 pm, Edward Rawde wrote:

"Edward Rawde" <invalid@invalid.invalid> wrote in message news:vf2569$2f0q$1@nnrp.usenet.blueworldhosting.com...

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vf20si$96u8$1@dont-email.me...

On 20/10/2024 3:36 am, Edward Rawde wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vevqip$3q3dn$1@dont-email.me...

On 19/10/2024 2:03 pm, Edward Rawde wrote:

"john larkin" <JL@gct.com> wrote in message news:j656hjp1rq659uh61k3q75bipaf386qqh1@4ax.com...

On Fri, 18 Oct 2024 18:58:43 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>

"Jeroen Belleman" <jeroen@nospam.please> wrote in message news:veumn5$3fbqu$1@dont-email.me...

On 10/18/24 23:19, Edward Rawde wrote:

"Cursitor Doom" <cd999666@notformail.com> wrote in message news:veuirv$3cmo3$10@dont-email.me...

On Fri, 18 Oct 2024 15:59:09 -0400, Edward Rawde wrote:
>

"Cursitor Doom" <cd999666@notformail.com> wrote in message
news:veucs2$3cmo3$9@dont-email.me...

On Fri, 18 Oct 2024 14:20:48 -0400, Edward Rawde wrote:
>

"Cursitor Doom" <cd999666@notformail.com> wrote in message
news:veu7kt$3cmo3$8@dont-email.me...

On Fri, 18 Oct 2024 13:47:02 -0400, Edward Rawde wrote:
>

"Cursitor Doom" <cd999666@notformail.com> wrote in message
news:veu45s$3cmo3$5@dont-email.me...

On Fri, 18 Oct 2024 11:25:19 -0400, Edward Rawde wrote:
>

"piglet" <erichpwagner@hotmail.com> wrote in message
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Edward Rawde <invalid@invalid.invalid> wrote:

<snip>
This will probably mess up the thread structure, but here's another variation. It struck me that the current spike being pulled from the amp through D1 is probably messing up the op amp's output stage, so I decided to buffer the op amp output with a PNP to minimise this.
The 4th harmonic is now almost 50dB below the fundamental.
You could probably do even better with a more elaborate circuit that kept the output frequency away from the gate  of the FET. My more ambitious simulation put in a precision rectifier to get a DC output that I could compare with a voltage reference with an integrator, whose output was low pass filtered before it went into the AD734 to adjust the gain.
A pure integrator would introduce too much phase shift to allow a stable control loop, so there was a resistor in series with the integrating capacitor to give you a sensible settling time for the loop.
That wasn't any kind of low cost approach.
Version 4
SHEET 1 2196 916
WIRE -352 -608 -480 -608
WIRE 128 -608 -352 -608
WIRE 464 -608 128 -608
WIRE 464 -576 464 -608
WIRE 464 -480 464 -496
WIRE 464 -480 320 -480
WIRE 320 -416 320 -480
WIRE -160 -256 -256 -256
WIRE -80 -256 -160 -256
WIRE -16 -256 -80 -256
WIRE 48 -256 -16 -256
WIRE 160 -256 112 -256
WIRE 240 -256 224 -256
WIRE 320 -256 320 -336
WIRE 320 -256 304 -256
WIRE -160 -240 -160 -256
WIRE -256 -224 -256 -256
WIRE -16 -176 -16 -256
WIRE -256 -128 -256 -160
WIRE -160 -128 -160 -160
WIRE -160 -128 -256 -128
WIRE -80 -128 -160 -128
WIRE -48 -128 -80 -128
WIRE 80 -128 48 -128
WIRE 160 -128 80 -128
WIRE 256 -128 240 -128
WIRE 320 -128 256 -128
WIRE 448 -128 400 -128
WIRE -80 -64 -80 -128
WIRE -32 -64 -80 -64
WIRE 64 -64 48 -64
WIRE 80 -64 80 -128
WIRE 80 -64 64 -64
WIRE 256 64 256 -128
WIRE 256 64 48 64
WIRE -480 80 -480 -608
WIRE 128 96 128 -608
WIRE -352 112 -352 -608
WIRE 48 112 48 64
WIRE 96 112 48 112
WIRE 432 128 160 128
WIRE 448 128 448 -128
WIRE 448 128 432 128
WIRE 528 128 528 -432
WIRE 528 128 448 128
WIRE 608 128 528 128
WIRE 656 128 608 128
WIRE 96 144 -80 144
WIRE -80 224 -80 144
WIRE 16 224 -80 224
WIRE 224 224 16 224
WIRE 304 224 288 224
WIRE 432 224 432 128
WIRE 432 224 384 224
WIRE -80 240 -80 224
WIRE 16 240 16 224
WIRE -480 320 -480 160
WIRE -480 320 -560 320
WIRE -560 336 -560 320
WIRE -480 336 -480 320
WIRE -352 336 -352 176
WIRE -352 336 -480 336
WIRE -336 336 -352 336
WIRE -256 336 -256 -128
WIRE -256 336 -336 336
WIRE -80 336 -80 320
WIRE -80 336 -256 336
WIRE 16 336 16 304
WIRE 16 336 -80 336
WIRE -480 464 -480 336
WIRE -336 496 -336 336
WIRE -480 656 -480 544
WIRE -336 656 -336 560
WIRE -336 656 -480 656
WIRE 128 656 128 160
WIRE 128 656 -336 656
WIRE 464 656 464 -384
WIRE 464 656 128 656
FLAG -560 336 0
FLAG -80 -256 FET_gate
FLAG 64 -64 TP
FLAG 608 128 output
SYMBOL voltage -480 64 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=0.1
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL res 352 224 R90
WINDOW 0 -20 5 VBottom 2
WINDOW 3 21 -5 VTop 2
SYMATTR InstName R1
SYMATTR Value 10.5k
SYMBOL cap 288 208 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 15n
SYMBOL cap 32 304 R180
WINDOW 0 -33 54 Left 2
WINDOW 3 -49 18 Left 2
SYMATTR InstName C2
SYMATTR Value 15n
SYMBOL polcap -368 112 R0
SYMATTR InstName C4
SYMATTR Value 100l
SYMBOL OpAmps\LT1057 128 64 R0
SYMATTR InstName U2
SYMBOL res -160 -208 R0
SYMATTR InstName R6
SYMATTR Value 47k
SYMBOL res 208 -128 R90
WINDOW 0 -21 6 VBottom 2
WINDOW 3 18 3 VTop 2
SYMATTR InstName R7
SYMATTR Value 6.34k
SYMBOL res 368 -128 R90
WINDOW 0 -17 16 VBottom 2
WINDOW 3 15 7 VTop 2
SYMATTR InstName R8
SYMATTR Value 13k
SYMBOL diode 48 -240 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL res 320 -368 R180
WINDOW 0 15 28 Left 2
WINDOW 3 15 -8 Left 2
SYMATTR InstName R9
SYMATTR Value 4.7k
SYMBOL njf 48 -176 R90
WINDOW 0 -38 17 VRight 2
WINDOW 3 -7 -47 VRight 2
SYMATTR InstName J1
SYMATTR Value 2N3819
SYMBOL voltage -480 448 R0
WINDOW 123 0 0 Left 0
WINDOW 39 10 135 Left 2
WINDOW 0 383 -483 Left 2
WINDOW 3 15 104 Left 2
SYMATTR SpiceLine Rser=0.1
SYMATTR InstName V2
SYMATTR Value 12
SYMBOL polcap -352 496 R0
SYMATTR InstName C5
SYMATTR Value 100l
SYMBOL res -80 272 R0
SYMATTR InstName R2
SYMATTR Value 10.5k
SYMBOL polcap -240 -160 R180
WINDOW 0 24 57 Left 2
WINDOW 3 24 8 Left 2
SYMATTR InstName C3
SYMATTR Value 10µ
SYMBOL res 16 -64 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 330
SYMBOL FerriteBead 192 -256 R90
WINDOW 0 -16 0 VBottom 2
SYMATTR InstName L1
SYMATTR Value 14µ
SYMATTR SpiceLine Ipk=3 Rser=0.0122 Rpar=870 Cpar=1000f
SYMBOL FerriteBead 272 -256 R90
WINDOW 0 -16 0 VBottom 2
SYMATTR InstName L2
SYMATTR Value 14µ
SYMATTR SpiceLine Ipk=3 Rser=0.0122 Rpar=870 Cpar=1000f
SYMBOL pnp 528 -384 R180
SYMATTR InstName Q1
SYMATTR Value 2N2907
SYMBOL res 464 -544 R0
SYMATTR InstName R4
SYMATTR Value 4.7k
TEXT -184 472 Left 2 !.tran 0 20s 0s startup
--
Bill Sloman, Sydney