Astable multivibrator has a great significance so was used wide in variety of Electronic circuits.And mostly we employ NE 555 Timer IC as an Astable multivibrator but here in this square wave generator we use a Operational Amplifier (Op-Amp) as a multivibrator.This circuit works in a very simple manner and it was very cheap to construct one.
WORKING OF SQUARE WAVE GENERATOR:
This multivibrator works in same way as a comparator by comparing the two input voltages and giving the output signals regarding the input voltage values.When the circuit is switched ON the C1 starts charging through the Resistors R1 and R2.The Resistor R2 was a variable one and it was used to change the frequency range of the output signal.When the voltage across the Capacitor rises above the junction R3 and R4 the output switches to fully negative voltage.C1 will begin to discharge and charges in the opposite direction.
When the negative voltage across the C1 falls below that pin 3 the circuit switches back quickly to the fully positive output value thereby giving out the high signal.The above cycle repeats endlessly resulting in giving out a series of square wave pulses as output through the Pin 3.The value of capacitor should be around 1uf and this circuit is capable of giving out output signal of frequency of (1Hz-25Hz).
This circuit will be a great alternative for other Astable multivibrator circuits and cheap one too.I hope this circuit and explanation will be useful to you and you are welcome to share your opinions and views regarding this post.Master the art of Electronics with us.