Hi, I need to design a sawtooth wave oscillator, and I found this design from http://hobby_elec.piclist.com/e_ckt17.htm

does anyone can show me how to get the equation, f=(1/2C(R1+R2))x(R3/R4) and also the osillator is valid for what range of the frequency, thanks.

 

I believe the formula is worked out, and a frequency of 56.8 Hz is obtained. Try changing component values to see what range can be obtained.