Astable Multivibrator using 555
However, the Set and Reset time durations will not be equal to this circuit. The resistors Ra and Rb are involved in charging the capacitor but, only resistor Rb is involved in discharging period. So, charging time will definitely be more than discharging time i.e.., TON is more than TOFF. Hence, this circuit can be used to generate clock pulses for digital circuits or where the frequency is the parameter rather than the duty ratio.
Astable with Equal Ton and Toff
This is called a Square wave generator, which can be used to generate musical notes by setting the frequency of the wave at the desired musical note. For example, setting the frequency at 440 Hz and connecting the speaker at the output in proper configuration gives the musical note ‘A’ of the musical piano. This note is used as a tuning standard.
Simulation – Waveforms of Astable Multi-vibrator
Astable Multivibrators are the most commonly used type of multivibrator circuit. An astable multivibrator is a free-running oscillator that has no permanent “meta” or “steady” state but is continually changing its output from one state (LOW) to another state (HIGH) and then back again.