Here am going to explain sawtooth waveform generator using op-amp. sawtooth waveform can be also generated by an asymmetrical astable multivibrator followed by an integrator The sawtooth wave generators have wide application in time-base generators and pulse width modulation circuits.
The difference between the triangular wave and sawtooth waveform is that the rise time of triangular wave is always equal to its fall of time while in saw tooth generator, rise time may be much higher than its fall of tim , vise versa . The triangular wave generator can be converted in to a sawtooth wave generator by injencting a variable dc voltage into the non inverting terminal of the integrator.
In this circuit a potentiometer is used (47K) . Use of the potentiometer is when the wiper moves towards -V ,the rise tim of the sawtooth become longerthan the fall time. If the wiper moves towards +V , the fall time becomes more than the rise time.
Reason is when comparator output is at -ve saturaion. When wiper moves to -ve supply, a negative voltage is added to inverting terminal. This causes the potential difference across R1 decreases and hence the current through the resistor and capacitor decreases . Then slope of the output, I/C decreases and un tern rise time decreases. When the compartor output goes positive , due to presence of negative voltage at the inverting terminal, potential difference of across the resistor R1 increases and hebce cyrrent increases. Then slope increases and fall time decreases. And obtained output as sawtooth wave.
Components for wiring this circuit
Op-amp ic - 741C
R1 - 1K
R2 - 180 Ω
R3 - 12K
R - 47K
C - 0.1μF