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With one double operational amplifier and a MOSFET transistor, a high quality low
frequency can be done a sine oscillator. The operational amplifier is connected in a
classic Wien bridge with positive feedback. The FET transistor directs the oscillations
and ensures a stable oscillation of the oscillator.
Assuming that R = R2 = R3 and C = C1 = C2, the output frequency can be calculated
from:
If a continuously tunable oscillator is required, a double tuning capacitor from old radio receivers can be used instead of C1 and C2.
The second option is to use a tandem, double potentiometer instead of R2 and R3.
Although this design can be implemented on a non-solderable field, I recommend implementation on a printed circuit board rather than a non-solderable field.
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