Astable Multivibrator Using 555 Timer Theory. The designing and working of astable multivibrator using a 555 timer ic is done by using ransistors and operational amplifiers. The 555 timer is a commonly used ic designed to produce a variety of output waveforms with the addition of an external rc network we have seen that multivibrators and cmos oscillators can be easily constructed from discrete components to produce relaxation oscillators for generating basic square wave output waveforms.
8th pin and 1st pin of the ic are used to give power vcc and gnd respectively. The modulating signal is applied at the pin 5 of the first ic 555 that is operating in astable mode. Astable multivibrator using 555 circuit astable multivibrator using 555 timer circuit diagram.
The above figure shows the 555 timer connected as an astable multivibrator.
A capacitor which are externally connected to the 555 timer. In this 555 astable multivibrator circuit led will switch on and off automatically with a particular duration. The 4th pin is reset pin which is active low and is connected to vcc to avoid accidental resets. On time off time frequency etc can be calculated using above formulas.
