Here capacitor C3 and diode D2 are connected in forward biased condition and used to amplify the signals. Diode D1 is used to protect the C3 from complete discharge. The following capacitor C4 therefore gets charged with a combined voltage from C3 and power supply. Therefore in this circuit, components like C3, C4, D1 and D2 are used to boost the input power.
Filed Under: 555 Timers, Electronic Projects