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

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>