Sawtooth wave oscillator is used in cathode ray tube deflection circuitry, in a PWM modulator, or in a analog to digital conversion. You can also use it in your own design, only your imagination can limit its application. Here is one example of the circuit:

sawtooth wave oscillator circuit schematic

The frequency is determined by C1, R1, R2, R3, and R4.  This frequency formula can be used to compute the frequency:

f = (1/2C(R1+R2))x(R3/R4)

Be aware if the real frequency will be slightly different since the formula is only an approximation, and the components values might deviate at some tolerance.