Re: AF Osc AGC alternatives to lamp/thermistor/FET

"piglet" <erichpwagner@hotmail.com> wrote in message news:vf3nie$i4vk$1@dont-email.me...

On 20/10/2024 7:54 pm, Edward Rawde wrote:

"piglet" <erichpwagner@hotmail.com> wrote in message news:vf2vp7$e446$1@dont-email.me...

Yesterday in the thread "Random thoughts on sinewave oscillators" I posted a LT Spice wirelist showing amplitude levelling
without
fet, ntc thermistor or ptc filament instead using current steering long tail pair - kinda poor mans multiplier.
>
Here is another alternative, using diode conductance bridge "variolosser".
>

>
Conversion to single rail allows V3 to be a standard zener.
>

...

>
Thanks, if you make the bridge diodes a pair in series (so 8 in the bridge instead of 4) then harmonic distortion should be
improved somewhat.
>
You might be able to finesse the long tail pair idea into lower distortion too.
>
piglet
>

Adding more diodes seemed to reduce it by about 3dB
So I went to extremes and also adjusted R5 and R6.

Like the FET circuit it seems that lowest distortion occurs when it's on the edge of not working at all.

Version 4
SHEET 1 1656 1236
WIRE 288 -208 -32 -208
WIRE 464 -208 288 -208
WIRE 608 -208 544 -208
WIRE 672 -208 608 -208
WIRE 880 -208 736 -208
WIRE 960 -208 880 -208
WIRE 1056 -208 960 -208
WIRE 608 -176 608 -208
WIRE -400 -144 -400 -176
WIRE -288 -144 -400 -144
WIRE 880 -144 880 -208
WIRE 960 -128 960 -208
WIRE -32 -112 -32 -208
WIRE -400 -96 -400 -144
WIRE -288 -96 -288 -144
WIRE 608 -64 608 -112
WIRE 1056 -64 1056 -208
WIRE 1200 -64 1200 -112
WIRE 880 0 880 -64
WIRE 960 0 960 -64
WIRE -288 16 -288 -32
WIRE -32 16 -32 -32
WIRE -400 32 -400 -16
WIRE 752 48 752 16
WIRE 1056 64 1056 16
WIRE 1056 64 784 64
WIRE 688 80 448 80
WIRE 720 80 688 80
WIRE 1104 96 784 96
WIRE 1200 96 1200 16
WIRE 1200 96 1104 96
WIRE 288 128 288 -208
WIRE 448 128 448 80
WIRE 176 144 176 112
WIRE 144 160 -160 160
WIRE 752 160 752 112
WIRE 288 176 288 128
WIRE 288 176 208 176
WIRE 1104 176 1104 96
WIRE 1200 176 1200 96
WIRE -688 192 -688 160
WIRE -32 192 -32 80
WIRE 32 192 -32 192
WIRE 144 192 32 192
WIRE -400 208 -608 208
WIRE 288 224 288 176
WIRE 688 240 688 80
WIRE 848 240 688 240
WIRE 1056 240 1056 64
WIRE 1056 240 912 240
WIRE 32 256 32 192
WIRE 176 256 176 208
WIRE 448 256 448 208
WIRE 448 256 384 256
WIRE 512 256 448 256
WIRE -512 272 -512 176
WIRE -608 288 -608 208
WIRE -544 288 -608 288
WIRE 384 288 384 256
WIRE 512 288 512 256
WIRE 1104 288 1104 240
WIRE 1200 288 1200 240
WIRE -400 304 -400 208
WIRE -400 304 -480 304
WIRE -288 304 -400 304
WIRE -240 304 -288 304
WIRE -32 304 -32 192
WIRE -688 320 -688 272
WIRE -608 320 -688 320
WIRE -544 320 -608 320
WIRE 688 336 688 240
WIRE -688 368 -688 320
WIRE -608 384 -608 320
WIRE -512 400 -512 336
WIRE 384 400 384 352
WIRE 512 400 512 352
WIRE -32 432 -32 384
WIRE 32 432 32 320
WIRE -608 480 -608 448
WIRE -688 496 -688 448
WIRE 384 512 384 464
WIRE 512 512 512 464
WIRE 288 608 288 304
WIRE 384 608 384 576
WIRE 384 608 288 608
WIRE 512 608 512 576
WIRE 560 608 512 608
WIRE 384 656 384 608
WIRE 512 656 512 608
WIRE 384 752 384 720
WIRE 512 752 512 720
WIRE -160 800 -160 160
WIRE 288 800 288 608
WIRE 288 800 -160 800
WIRE 288 848 288 800
WIRE 384 848 384 816
WIRE 512 848 512 816
WIRE 688 912 688 416
WIRE 896 912 688 912
WIRE 384 960 384 912
WIRE 448 960 384 960
WIRE 512 960 512 912
WIRE 512 960 448 960
WIRE 688 960 688 912
WIRE 288 992 288 928
WIRE 448 992 448 960
WIRE 800 1104 800 1072
WIRE 896 1120 896 912
WIRE 896 1120 832 1120
WIRE 448 1136 448 1072
WIRE 688 1136 688 1040
WIRE 688 1136 448 1136
WIRE 768 1136 688 1136
WIRE 880 1152 832 1152
WIRE 896 1152 880 1152
WIRE 800 1216 800 1168
FLAG -400 -176 PRail
FLAG 176 112 PRail
FLAG -400 32 0
FLAG 288 128 OUT
FLAG 752 16 PRail
FLAG 800 1072 PRail
FLAG 960 0 0
FLAG 32 432 0
FLAG 176 256 0
FLAG -32 432 Half
FLAG -288 304 Half
FLAG -688 496 0
FLAG -688 160 PRail
FLAG 288 992 Half
FLAG 880 0 Half
FLAG 752 160 0
FLAG 800 1216 0
FLAG 880 1152 Half
FLAG 560 608 Half
FLAG 1200 288 0
FLAG 1200 -112 PRail
FLAG 608 -64 Half
FLAG -512 400 0
FLAG -512 176 PRail
FLAG -608 480 0
FLAG -288 16 0
FLAG 1104 288 0
SYMBOL voltage -400 -112 R0
WINDOW 123 0 0 Left 0
WINDOW 39 -147 49 Left 2
WINDOW 0 -78 25 Left 2
WINDOW 3 19 2 Left 2
SYMATTR SpiceLine Rser=0.1
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL res 272 208 R0
SYMATTR InstName R3
SYMATTR Value 3300
SYMBOL res 272 832 R0
SYMATTR InstName R4
SYMATTR Value 2200
SYMBOL diode 368 288 R0
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL diode 368 848 R0
SYMATTR InstName D2
SYMATTR Value 1N914
SYMBOL diode 496 288 R0
SYMATTR InstName D3
SYMATTR Value 1N914
SYMBOL diode 496 848 R0
SYMATTR InstName D4
SYMATTR Value 1N914
SYMBOL res 432 112 R0
SYMATTR InstName R5
SYMATTR Value 75k
SYMBOL res 432 976 R0
SYMATTR InstName R6
SYMATTR Value 75k
SYMBOL res 704 432 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R8
SYMATTR Value 10k
SYMBOL res 704 1056 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R9
SYMATTR Value 10k
SYMBOL res 560 -224 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R7
SYMATTR Value 2200
SYMBOL res 896 -48 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R10
SYMATTR Value 470k
SYMBOL cap 944 -128 R0
SYMATTR InstName C4
SYMATTR Value 2000n
SYMBOL diode 624 -112 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D5
SYMATTR Value 1N914
SYMBOL diode 672 -192 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D6
SYMATTR Value 1N914
SYMBOL res -48 -128 R0
SYMATTR InstName R1
SYMATTR Value 15k
SYMBOL cap -48 16 R0
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL cap 16 256 R0
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL res -48 288 R0
WINDOW 3 34 76 Left 2
SYMATTR Value 15k
SYMATTR InstName R2
SYMBOL res 1040 -80 R0
SYMATTR InstName R11
SYMATTR Value 10k
SYMBOL OpAmps\LT1058 800 1072 M0
WINDOW 0 29 34 Left 2
SYMATTR InstName U5
SYMBOL OpAmps\LT1058 176 112 R0
SYMATTR InstName U1
SYMBOL OpAmps\LT1058 752 16 M0
WINDOW 0 39 6 Left 2
WINDOW 3 33 33 Left 2
SYMATTR InstName U2
SYMBOL OpAmps\LT1058 -512 240 R0
SYMATTR InstName U3
SYMBOL res -704 176 R0
SYMATTR InstName R12
SYMATTR Value 10k
SYMBOL res -704 352 R0
SYMATTR InstName R13
SYMATTR Value 10k
SYMBOL res 1184 -80 R0
SYMATTR InstName R14
SYMATTR Value 4.7k
SYMBOL zener 1216 240 R180
WINDOW 0 24 64 Left 2
WINDOW 3 -149 63 Left 2
SYMATTR InstName D7
SYMATTR Value BZX84C6V2L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL cap 912 224 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C3
SYMATTR Value 100n
SYMBOL cap -624 384 R0
SYMATTR InstName C5
SYMATTR Value 100n
SYMBOL polcap -304 -96 R0
SYMATTR InstName C7
SYMATTR Value 100�
SYMBOL cap 1088 176 R0
SYMATTR InstName C8
SYMATTR Value 100n
SYMBOL diode 368 400 R0
SYMATTR InstName D8
SYMATTR Value 1N914
SYMBOL diode 496 400 R0
SYMATTR InstName D9
SYMATTR Value 1N914
SYMBOL diode 368 656 R0
SYMATTR InstName D10
SYMATTR Value 1N914
SYMBOL diode 496 656 R0
SYMATTR InstName D11
SYMATTR Value 1N914
SYMBOL diode 368 512 R0
SYMATTR InstName D12
SYMATTR Value 1N914
SYMBOL diode 496 512 R0
SYMATTR InstName D13
SYMATTR Value 1N914
SYMBOL diode 368 752 R0
SYMATTR InstName D14
SYMATTR Value 1N914
SYMBOL diode 496 752 R0
SYMATTR InstName D15
SYMATTR Value 1N914
TEXT -352 872 Left 2 !.tran 0 2 1 startup
TEXT 992 704 Left 2 ;EPW SED OCT 2024
TEXT 992 744 Left 2 ;DIODE BRIDGE VARIOLOSSER AGC FOR WIEN BRDG OSC
TEXT 992 784 Left 2 ;Single rail conversion by Edward Rawde, Oct 20 2024