Triangular wave oscillator and output waveform using two operational amplifiers

 The sawtooth wave signal generator is actually an extension and application of the relaxation oscillator circuit. The figure shows a typical relaxation oscillator and output voltage
triangle waveform. If the input terminal of the operational amplifier switches between + and - voltage, the output terminal will have a triangular wave signal and an output voltage triangular
wave waveform. This feature can be used to form the required oscillation circuit.
    When the switch is switched to position 1, a negative voltage is applied, and a positive slope voltage is output. {When the switch is switched to position 2, a
negative slope voltage is output. If the switch switches back and forth at regular intervals, the output is
a triangle wave consisting of alternating positive and negative ramp voltages . One practical application of the relaxation oscillator is to use a voltage comparator to perform the switching function. The figure shows a triangle wave oscillator composed of
    two op amps and its output waveform .     First, assume that the output voltage of the comparator is the maximum negative potential. At this time, the output is connected to the inverting input terminal of the relaxation oscillator via Ri, and a positive-phase ramp voltage is generated at the output terminal of the relaxation oscillator. When the ramp voltage value reaches the upper trigger point, the input terminal of the comparator also obtains the maximum positive potential value. This positive potential causes the ramp voltage of the relaxation oscillator to gradually decrease from its highest point and change to the negative voltage direction. The ramp voltage continues to decrease in this direction until the lower trip point of the comparator. Then the input of the comparator also drops to the maximum negative potential, and then the cycle continues to be repeated, outputting a continuous triangle wave .