Ramp Signal Generator Using 555-Timer
The astable multivibrator with discharge terminal connected to the threshold terminal offers the least resistance during discharge period of the capacitor. This gives a sharp negative edge during the discharge period. A transistor is included in the charging path of the capacitor. As the capacitor voltage increases, because of the parallel path through resistors at the base of the transistor, the capacitor charges almost in a linear fashion. Thus linear ramp signal is generated across the timing capacitor.
Waveform of Ramp Signal Generator