Basically, this sine wave generator circuit is using op-amp (TL082) to generate the triangle wave and then convert the triangle wave into sine wave. This circuit will have upper frequency limit where limit op-amp slew rate.
[Note] this actual circuit component is difference from simulation.
The U2 is configure become comparator circuit, U1 is integrator, U3 is amplifier and U4 is buffer or amplifier.
The U1 and U2 is oscillator circuit, where, the U2 try to compare the U1 voltage with ground and generate the square wave, the U2 output is control by R3 and R2 value. The U1 is integrator circuit, the R1 and C1 is component that control the triangle wave rise and fall time. The rise time and fall time will affect the triangle wave frequency.
The triangle to sine wave converter circuit, input voltage must be around 4V (the triangle wave peak), to get nice sine wave. If the input wave is lower than 4V, the output still triangle wave. If the input wave is higher than 4V, the sine wave will distorted.
You can adjust the R2 value to control the triangle wave amplitude. Please notice the triangle wave frequency, it may affect by R2 value. The best solution to control the triangle wave amplitude without affect the oscillator frequency, is add in the amplifier (U3). By changing the U3 gain is will affect the sine wave quality. Using difference part of diode in triangle to sine wave converter, the input triangle peak requirement may change.
The last stage is U4 buffer or amplifier. the R6 is resistor to control the sine wave peak voltage. It will reduce the loading affect to converter circuit.
Output Signal:-
