Signal Generator Function 12V Sine Sawtooth Square Triangle ramp Rademacher function circuit Fourier transform

https://how2electronics.com/square-wave-generator-circuit-op-amp-741/

https://how2electronics.com/triangular-wave-generator-circuit-op-amp-741/

https://www.gadgetronicx.com/function-generator-circuit-diagram/ 

Signal Generator  Function 12V Sine  Sawtooth Square Triangle ramp 4QD-TEC