i've attached 555 sawtooth generator with sawtooth signal appeared at pin 6 of the second 555), i need to discuss about this schematic concerning the principle of generating such signal using 555.
When the 2nd 555 is triggered by the 1st 555, the PNP transistor applies a constant current to linearily charge the capacitor up to the pin 6 threshold voltage then pin 7 quickly discharges the capacitor.