Re: Random thoughts on sinewave oscillators

On 18/10/2024 6:47 pm, 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
news:vetde5$38sbk$1@dont-email.me...

Edward Rawde <invalid@invalid.invalid> wrote:

>
The circuit below produces a reasonable looking sinewave but the rise
time still seems to be slower than the fall time. It may be that the
amplifier in use is not ideal for this.
>
>

Could that just be second harmonic distortion? You could test the
amplifier by uncoupling the Wien network and injecting test inputs.
>
Elsewhere I think your amplitude control problems could be simply due
to too much gain.

>
Perhaps, but I've not so far been able to get the circuit I posted in
response to Bill to produce a sine wave no matter what I do with the
control loop gain.
It either grows to clipping or dies.

>
That's the main purpose behind having a thermistor or filament bulb in the
f/b path.

 Sure, but why use thermistors or filaments if you don't have to?
Filaments don't last forever, particularly not if you drop your equipment, and filaments make me think of something like a 5U4.
I forget when I last saw a filament. House lamps don't even have them now.
 I'm trying to make a low cost oscillator which produces the cleanest 1K Hz sinewave I can get, using only resistors, capacitors and
semiconductors.
 There are plenty of examples online, but some of them don't seem to simulate.
Whether that's because they do work in reality but not in simulation is hard to say.
 

Filaments, NTC thermistors and LDRs are awkward I agree. Sadly even JFETs are less mainstream than before. Here is an illustration I made showing a BJT long tail pair current steering the collector current of a basic ladder RC phase shift osc. Q1 is the oscillator and Q2-Q3 divert current into the load resistance as AGC directs.
Version 4
SHEET 1 1480 680
WIRE 352 -352 304 -352
WIRE 560 -352 352 -352
WIRE -608 -336 -608 -432
WIRE -496 -336 -496 -432
WIRE 304 -320 304 -352
WIRE 928 -272 928 -320
WIRE -128 -240 -128 -352
WIRE 0 -192 -64 -192
WIRE 112 -192 0 -192
WIRE 304 -192 304 -240
WIRE 304 -192 176 -192
WIRE 928 -176 928 -208
WIRE -608 -128 -608 -256
WIRE -496 -128 -496 -256
WIRE -352 -96 -368 -96
WIRE -128 -96 -128 -144
WIRE -128 -96 -352 -96
WIRE 304 -96 304 -192
WIRE 560 -96 560 -352
WIRE 0 -80 0 -192
WIRE 240 -48 144 -48
WIRE 672 -48 624 -48
WIRE 752 -48 672 -48
WIRE 800 -48 752 -48
WIRE 928 -48 928 -96
WIRE 928 -48 864 -48
WIRE -128 -32 -128 -96
WIRE 672 -16 672 -48
WIRE 752 -16 752 -48
WIRE 144 0 144 -48
WIRE 304 32 304 0
WIRE 432 32 304 32
WIRE 560 32 560 0
WIRE 560 32 432 32
WIRE 928 32 928 -48
WIRE 0 64 0 0
WIRE -608 112 -608 32
WIRE -496 112 -496 32
WIRE -128 112 -128 48
WIRE -128 128 -128 112
WIRE 144 128 144 80
WIRE 432 160 432 32
WIRE 672 160 672 64
WIRE 752 160 752 48
WIRE 928 160 928 96
WIRE -368 208 -368 -96
WIRE -256 208 -368 208
WIRE -128 208 -176 208
WIRE -80 208 -128 208
WIRE 64 208 0 208
WIRE 112 208 64 208
WIRE 240 208 192 208
WIRE 368 208 240 208
WIRE -608 240 -608 192
WIRE -496 240 -496 192
WIRE -128 288 -128 208
WIRE 64 288 64 208
WIRE 240 288 240 208
WIRE 432 304 432 256
WIRE 528 304 432 304
WIRE 528 320 528 304
WIRE 432 336 432 304
WIRE -128 368 -128 352
WIRE 64 368 64 352
WIRE 240 368 240 352
WIRE 528 416 528 384
WIRE 432 448 432 416
WIRE 528 528 528 496
FLAG -128 368 0
FLAG 64 368 0
FLAG 240 368 0
FLAG 528 528 0
FLAG -608 -128 0
FLAG 144 128 0
FLAG -608 240 0
FLAG -608 -432 P10
FLAG 352 -352 P10
FLAG -608 32 N10
FLAG 432 448 N10
FLAG -128 112 N10
FLAG -496 240 0
FLAG -496 32 N5
FLAG -496 -128 0
FLAG -496 -432 P5
FLAG 0 64 0
FLAG 928 160 0
FLAG 752 160 0
FLAG -352 -96 OUT
FLAG 928 -320 OUT
FLAG -128 -352 P10
FLAG 672 160 0
SYMBOL voltage -608 -352 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 10
SYMBOL npn 368 160 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL npn 240 -96 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL npn 624 -96 M0
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res 288 -336 R0
SYMATTR InstName R6
SYMATTR Value 22k
SYMBOL res 416 320 R0
SYMATTR InstName R4
SYMATTR Value 22k
SYMBOL res 208 192 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 47k
SYMBOL res 16 192 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 47k
SYMBOL res -160 192 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 47k
SYMBOL cap -144 288 R0
SYMATTR InstName C1
SYMATTR Value 10n
SYMBOL cap 48 288 R0
SYMATTR InstName C2
SYMATTR Value 10n
SYMBOL cap 224 288 R0
SYMATTR InstName C3
SYMATTR Value 10n
SYMBOL cap 512 320 R0
SYMATTR InstName C4
SYMATTR Value 0.01m
SYMBOL npn -64 -240 M0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL res -112 -48 M0
SYMATTR InstName R10
SYMATTR Value 3300
SYMBOL cap 912 -272 R0
SYMATTR InstName C6
SYMATTR Value 100n
SYMBOL res 512 400 R0
SYMATTR InstName R5
SYMATTR Value 100
SYMBOL voltage 144 -16 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V5
SYMATTR Value 1
SYMBOL voltage -608 96 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value -10
SYMBOL res 912 -192 R0
SYMATTR InstName R8
SYMATTR Value 100k
SYMBOL res -16 -96 R0
SYMATTR InstName R9
SYMATTR Value 100k
SYMBOL cap 112 -176 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C7
SYMATTR Value 1000n
SYMBOL voltage -496 96 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V4
SYMATTR Value -5
SYMBOL voltage -496 -352 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL diode 864 -64 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D1
SYMATTR Value 1N914
SYMBOL diode 944 96 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D2
SYMATTR Value 1N914
SYMBOL cap 736 -16 R0
SYMATTR InstName C5
SYMATTR Value 1000n
SYMBOL res 656 -32 R0
SYMATTR InstName R7
SYMATTR Value 470k
TEXT -624 472 Left 2 !.tran 3000m startup
TEXT 920 480 Left 2 ;EPW SED OCT 2024
TEXT 664 536 Left 2 ;CURRENT STEER AGC ON LADDER RC OSC
piglet