On Tue, 8 Apr 2025 21:04:25 -0400, "Edward Rawde"
<
invalid@invalid.invalid> wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:vhabvj1uo56ikdhu8if219rvtfal6lijee@4ax.com...
On Tue, 8 Apr 2025 14:41:44 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:8099vjhs62eofoioejtlssoa19ifjrdvcg@4ax.com...
On Mon, 7 Apr 2025 22:46:13 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"Edward Rawde" <invalid@invalid.invalid> wrote in message news:vsso97$1imi$1@nnrp.usenet.blueworldhosting.com...
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:tcl2vjp49q4ga21itrpnmr4u3ts06vqffd@4ax.com...
On Fri, 4 Apr 2025 23:55:11 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:uop0vjp3d13t441ujfboi5aeeg08anm1je@4ax.com...
On Fri, 4 Apr 2025 16:29:27 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:add0vjdh2gcma0n9pfunq76n04cfbkhtnj@4ax.com...
On Fri, 4 Apr 2025 14:25:29 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vsnufh$2ou7j$1@dont-email.me...
On 4/04/2025 11:33 am, JM wrote:
On Thu, 3 Apr 2025 19:25:33 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:qq8tujlpciqc2jrd0ibljmjr9pd37ip6hi@4ax.com...
On Sun, 30 Mar 2025 14:54:56 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>
Not long ago JM posted a 1KHz sinewave oscillator with very low distortion.
It used a 470uF non polarized capacitor which in practice would probably be made from two 1000uF capacitors.
There's nothing wrong with that but I wanted to see whether I could make a working circuit without needing such a
large
capacitor.
....
>
Here's an almost fully practical circuit except for the current sources and sinks.
>
>
I reversed the polarity of the control feedback and applied it to the
inverting input of the first oscilllator stage, removed some
redundant capacitors, and added some filtering to the gain control
signal. Also altered some gain values to improve the dynamics (but
that still has to be addressed).
>
Most real world designs would use a sample and hold circuit to sample
the output at it's maximum point and use that to control the feedback,
similar to the topology I think I posted a while ago. It might be
worthwhile looking at that.
>
>
Thanks. That has the lowest distortion I've seen in a simulation so far.
>
I can't find the sample/hold circuit you mentioned, would you mind reposting it?
>
Thank you for your help with this. It is much appreciated.
>
>
>
>
Is the sample/hold circuit the one below?
>
After much digging I found it in a very interesting thread started by Bill Sloman on 5th February 2025 "The low distortion
oscillator problem".
>
I can't get it to simulate in 24.1.5
something to do with unknown parameter in table{-2m,0,2m,1}
>
Yes. Change the braces to brackets. Example use shown below. H2,3
should be circa -170(ish)dBc. Note that I have switched most op amps
outwith the control loop to simple models so that you can investigate
the control loop in isolation (it's fairly easy to implement the
sampling in hardware and it will be close to this in performance).
Compare the circuit below with one with the original polyphase
sampling (leave in the simple models) to determine any benefit. You
are already beyond the point where real opamps will limit the
performance - in this particular oscillator design.
Version 4
SHEET 1 3020 2548
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FLAG -704 80 0
FLAG -320 80 0
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FLAG -624 0 vcc
FLAG -624 64 vee
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FLAG -1216 848 vee
FLAG -144 -16 output
FLAG -2064 720 vcc
FLAG -2064 656 vee
FLAG -2208 1232 vee
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FLAG -1888 48 0
FLAG -1824 -128 vcc
FLAG -1824 -64 vee
FLAG -1888 -48 0
FLAG -2704 720 vcc
FLAG -2704 656 vee
FLAG -1904 1088 vmod+
FLAG -1312 800 0
FLAG -1552 -464 0
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FLAG -1776 592 0
FLAG -1888 832 vee
FLAG -1776 832 0
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FLAG -1520 256 0
FLAG -1904 976 vmod-
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FLAG -1920 512 0
FLAG -592 768 0
FLAG -688 768 0
FLAG -768 768 0
FLAG -912 384 0
FLAG -864 368 0
FLAG -768 320 vmod-
FLAG -1056 240 vmod+
SYMBOL res -992 -112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
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SYMATTR Value 10K
SYMBOL res -768 -112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 16K
SYMBOL res -352 -112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 16K
SYMBOL cap -592 -112 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL cap -224 -112 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL res -736 -368 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 10K
SYMBOL res -736 -208 M270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R5
SYMATTR Value 1.8Meg
SYMBOL cap -1392 512 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C3
SYMATTR Value 1u
SYMBOL res -1232 736 M180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
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SYMBOL res -1152 -112 R90
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WINDOW 3 32 56 VTop 2
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SYMBOL res -1408 624 R270
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WINDOW 3 0 56 VBottom 2
SYMATTR InstName R6
SYMATTR Value 47k
SYMBOL cap -1440 592 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C4
SYMATTR Value 10u
SYMBOL OpAmps\LT1679 -1408 736 M0
SYMATTR InstName U3
SYMBOL res -2144 848 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R23
SYMATTR Value 1k
SYMBOL npn -2144 640 M0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL res -2144 1072 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R24
SYMATTR Value 540K
SYMBOL current -2208 1152 M0
SYMATTR InstName I1
SYMATTR Value 1m
SYMBOL res -2032 960 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R26
SYMATTR Value 540K
SYMBOL current -2560 1152 R0
SYMATTR InstName I2
SYMATTR Value 1m
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SYMATTR InstName R27
SYMATTR Value 300
SYMBOL res -1968 432 M270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
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SYMATTR Value 15K
SYMBOL current -2144 -256 M0
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SYMATTR Value 650u
SYMBOL current -2624 -256 M0
SYMATTR InstName I4
SYMATTR Value 650u
SYMBOL res -1776 240 M270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
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SYMATTR Value 1k
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WINDOW 3 32 56 VTop 2
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SYMATTR Value 1k
SYMBOL cap -1792 304 R90
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WINDOW 3 32 32 VTop 2
SYMATTR InstName C13
SYMATTR Value 33p
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SYMATTR InstName Q2B
SYMATTR Value {BN}
SYMBOL npn -2432 224 M0
SYMATTR InstName Q2A
SYMATTR Value {BN}
SYMBOL npn -2336 224 R0
WINDOW 3 55 69 Left 2
SYMATTR Value {BN}
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SYMBOL npn -2688 224 R0
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SYMATTR Value {BN}
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SYMATTR Value 2N3904
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WINDOW 3 32 32 VTop 2
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WINDOW 39 0 0 Left 0
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SYMATTR Value 15
SYMBOL voltage -1504 -464 R0
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WINDOW 39 0 0 Left 0
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WINDOW 3 0 56 VBottom 2
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WINDOW 3 0 56 VBottom 2
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SYMATTR Value 1k
SYMBOL res -1568 112 M270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R25
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SYMBOL res -1504 112 M0
SYMATTR InstName R28
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WINDOW 3 18 51 Left 2
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SYMBOL OpAmps\LT1679 -2064 688 R180
WINDOW 3 16 46 Left 2
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SYMBOL schottky -1456 400 M90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D1
SYMATTR Value BAT54
SYMATTR Description Diode
SYMATTR Type diode
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SYMATTR Value 1N914
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SYMATTR SpiceLine Aol=5Meg
SYMATTR SpiceLine2 GBW=60Meg
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SYMATTR SpiceLine Aol=5Meg
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SYMATTR InstName U9
SYMATTR SpiceLine Aol=5Meg
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TEXT -2080 -600 Left 2 !.tran 0 5 0 1u uic
TEXT -2080 -632 Left 2 !.options plotwinsize=0 numdgt=15
TEXT -3208 -592 Left 2 !.MODEL BCM847BS NPN IS = 1.822E-14 NF = 0.9932
ISE= 2.894E-16 NE = 1.4 \n+ BF = 324.4 IKF = 0.109 VAF = 82 NR =
0.9931 ISC = 9.982E-12 NC = 1.763 \n+ BR = 8.29 IKR = 0.09 VAR = 17.9
RB = 10 IRB = 5E-06 RBM = 5 RE = 0.649 \n+ RC = 0.7014 CJE = 1.244E-11
VJE = 0.7579 MJE = 0.3656 TF = 4.908E-10 \n+ XTF = 9.51 VTF = 2.927
ITF = 0.3131 PTF = 0 CJC = 3.347E-12 VJC = 0.5463 \n+ MJC = 0.391 XCJC
= 0.6193 TR = 9E-08 CJS = 0 VJS = 0.75 MJS = 0.333 \n+ XTB = 0 XTI = 3
EG = 1.11 FC = 0.979
TEXT -2088 -456 Left 2 !.param BN=847
TEXT -2088 -488 Left 2 !.model 847 ako:BCM847BS
TEXT -2080 -552 Left 2 !.lib opamp.sub
Low distortion sinewave oscillator without big capacitor.
Re: Low distortion sinewave oscillator without big capacitor.