Voltage controlled sawtooth oscillatora

When the input terminal of the relaxation oscillator adopts an adjustable DC control voltage, the delta-crossing oscillator becomes a sawtooth wave oscillator. The voltage
control signal can be a sine wave or a non-sinusoidal wave. If the input signal terminal uses a controllable thyristor PUT in parallel with the feedback capacitor, so that each
ramp voltage is cut off at the specified level, as shown in the figure.
    First, the sawtooth oscillator starts with a negative DC input voltage -H. Produces a positive ramp at the output. When the output slope voltage of the anode of the controllable single thyristor
exceeds the gate voltage by 0.7 V, the single thyristor will trigger conduction. The gate voltage is set to a value approximately equal to the expected
peak voltage of the sawtooth waveform. When the PUT is turned on, the capacitor discharges quickly, as shown in Figure (b). Because of the PUT positive phase voltage VF, the capacitor
will not be completely discharged to zero. The discharge process continues until the current of the PUT is lower than the holding current. At this time, the thyristor will be cut off and the capacitor
will start charging again, thus generating a new output ramp voltage. This cycle keeps repeating. The output signal will be a repeating sawtooth
waveform. The amplitude and period of the sawtooth waveform can be adjusted by changing the PUrr gate voltage .