This is a simple function generator circuit that can produce thefollowing waveforms: square wave, triangular wave, and sinewave.The circuit’s main components are four 741 IC’s. The 741 is aop-amp IC. The first op amp in Figure is configured as anastablemultivibrator, which continuously generates a squarewave. Assume that C3 has no charge initially. The voltage at theinverting input is zero, while the voltage at the non-inverting inputis very slightly positive (a ratio of the op amp’s output offsetvoltage as determined by R3 and R2). This minute voltagedifference at the inputs is enough to cause the op amp’s output toswing to ‘high’.When the output becomes high, C3 starts charging up. Thevoltage at the inverting input soon exceeds that at the non-inverting input, forcing the output to swing to ‘low’, whichdischarges C3 again.
At a certain point, the voltage at the non-inverting input exceeds that at the inverting input again, and theoutput of the op amp goes high again.This cycle wherein the first op amp’s output swings between ‘low’and ‘high’ goes on indefinitely, generating the square wave.Thetwo middle op-amps are both configured as integrators. The inputto the second op amp is the square wave output of the first opamp. Being configured as an integrator, this op amp outputs atriangular wave (the integral of a square wave), as shown inFigure.The triangular wave output of the second op amp is then fed intothe third op amp, which is also configured as an integrator. Theoutput of the third op amp is a sine wave (the integral of atriangular wave).