First and second like resistances are serially connected across a reactance element. Where the reactance element is a capacitor, a constant voltage is applied to first one terminal and then to the other terminal of the capacitor such that the capacitor discharges and charges first in one direction and then in the opposite direction through the respective resistances. When the reactance element is an inductance, a constant voltage is applied to the inductance and the two resistances in a manner to alternately reverse the direction of flow of current through the inductance. A sawtooth wave is produced when the waveforms appearing at each terminal of the reactance element are summed together.