Square-wave Gen using uA 741

Description.

A wide range square wave generator using IC uA741 is shown here.The circuit uses positive feedback for Schmitt trigger action and negative feedback for timing of the wave form.

Let us presume that the output is high and the capacitor C1 is fully  discharged.C1 now starts charging via R2 and R1.When the voltage across C1 rises above that the Junction of R3 & R4,the output quickly switches to fully negative voltage.C1 now starts discharging and charges in the opposite direction.Again,when the negative voltage across C1 falls below that at pin 3,the circuit switches back quickly to the fully positive output value.The cycle repeats endlessly.
The frequency of the square wave can be varied by varying POT R1.The frequency range of the circuit depends on the value of R3,R4 & C1.
Circuit diagram with Parts list.

Notes.

• The circuit has to be powered from a +9/-9 V  DC dual power supply .
• The IC 1 must be mounted on  an IC base.
• The frequency of output can be varied by varying POT R1.
• The frequency range  can be adjusted by changing the value of R3,R4 or C1.
• The table given below gives the relationship between the values of C1 and the frequency range covered.