This is my circuit.It depends on how the amplitude is stabilized. There is more than one method.
Please post your oscillator circuit or a link to it.
The output amplitude is function of power supply voltage and opamp characteristics.
You could try controlling the amplitude by varying the power supply voltage, or you could try a circuit like the one below,, in which case you would put a resistor in series with the anode of D1 and sum current into the anode of D1 through another resistor to modify the ampltude.
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https://rustybolt.info/wordpress/wp-content/uploads/2012/01/WBO-JF10ZL.gif
The cleanest solution is probably to pass the output of the unmodified oscillator through a gain control circuit such as a transconductance multiplier or multiplying DAC.
(pdf) MT-079: Analog Multipliers
LM13700 OTA excellent VCA -
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjRwKnG5fDaAhUS6GMKHU0zAw8QFggnMAA&url=http://www.ti.com/lit/ds/symlink/lm13700.pdf&usg=AOvVaw15pmSw_PzWM7BLA6muLJ4V
Figure 20.
Regards, Dana.
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