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Date: Sun, 20 Oct 2024 14:25:33 -0400
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Subject: Re: AF Osc AGC alternatives to lamp/thermistor/FET
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On 10/20/2024 11:38 AM, john larkin wrote:
> On Sun, 20 Oct 2024 14:15:19 +0100, piglet <erichpwagner@hotmail.com>
> wrote:
> 
>> 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".
>>
>> For the full 1960s vibe replace U2 U3 with bjt current sources.
> 
> That's still limiting a Wein bridge, essentially a single-element
> resonator.
> 
> If you do the double-integrator type oscillator, you can do gain
> control on the first integrator, and then the second one adds 6
> dB/octave harmonic reduction.
> 
> I think you can even get 12 dB/octave harmonic reduction if you do the
> amplitude limiter right. 12*3 = 36!
> 
> 

There's probably a way to finagle the 4th section of an LM13700 to apply 
a bias current inversely proportional to the output level into pin IB1, 
here:

<https://imgur.com/a/xRVx2PC>