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Diagram for a Sine Wave Generator This is a circuit for generating a sine wave from a single operational amplifier. The feedback loop of the op amp in this circuit (741) consists of a twin-T filter connected between its output and its inverting input. Positive feedback for oscillation is provided by R2.    The twin-T filter (see Figure 2) is a passive notch filter composed of two T-networks, with maximum attenuation occurring at fn = 1/(2πRC) .  One of these T networks has one resistor and two capacitors, while the other has two resistors and one capacitor.    At the notch frequency fn of the twin-T filter, the total phase shift around the loop gain of this op amp circuit is zero, which satisfies the requirement for oscillation. This is why the circuit generates a sine wave with a frequency equal to fn = 1/(2πRC) .    Note that variable resistor R3 in the circuit needs to be adjusted (in relation to the chosen value for R) until oscillatio...

I have previously written quite a few articles on sinusoidal pulse width modulation (SPWM). I've discussed about how to generate the sine table, how to implement it, how to practically generate the SPWM signals (with example code) and also how to implement feedback with simple sine table manipulation with table pointer instead of complex PID control. All these methods have one thing in common regarding the implementation - use of the sine table and its control with the table pointer. Whether you use or implement feedback or not, the table pointer is used to access and retrieve values from the sine table. Before reading or going through this article, I suggest you go through these first: Tutorial (Click here to open tutorial): Generation and Implementation of Sine Wave Table   Article (Click here to open article): Smart Sine – Software to generate sine table Article (Click here to open article): Generation of sine wave using SPWM in PIC16F684 It took quite a while for me to unde...

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The proposed circuit generates accurately spaced PWM pulses which imitates a sine wave very closely and thus can be considered as good as its sine wave counter part design. Here we use  two stages for creating the required  PWM pulses, the stage comprising the ICs 741 and the other comprising the IC 555. Let’s learn the whole concept in details. How the Circuit Functions – The PWM Stage The circuit diagram can be understood with the following points: The two op amps are basically arranged to generate the required sample source voltages for the IC 555.  The couple of outputs from this stage is responsible for the generation of square waves and triangular waves. The second stage which is actually the heart of the circuit consists of the IC 555. Here the IC is wired in a monostable mode with the square waves from the op amp stage applied to its trigger pin #2 and the triangular waves applied to its control voltage pin # 5. The square wave input triggers the monostable to ge...

The proposed circuit generates accurately spaced PWM pulses which imitates a sine wave very closely and thus can be considered as good as its sine wave counter part design. Here we use two stages for creating the required PWM pulses, the stage comprising the ICs 741 and the other comprising the IC 555. Let’s learn the whole concept in details. How the Circuit Functions – The PWM Stage The circuit diagram of the proposed pure sine wave inverter can be understood with the following points: The two op amps are basically arranged to generate the required sample source voltages for the IC 555. The couple of outputs from this stage is responsible for the generation of square waves and triangular waves. The second stage which is actually the heart of the circuit consists of the IC 555. Here the IC is wired in a monostable mode with the square waves from the op amp stage applied to its trigger pin #2 and the triangular waves applied to its control voltage pin # 5. The square ...

This circuit is a sine wave oscillator which uses operational amplifiers working in oscillation back (positive feedback), or the oscillation output to the input. This oscillator is called Wien bridge circuit is often used. The oscillator Sine wave oscillator is difficult to be done due to the distortion of the oscillation signal, different oscillator square wave, triangle wave oscillator (sawtooth). Oscillator Sine wave Circuit Diagram In the case of C1 = C2 = C, R = R1 = R2, giving the frequency of oscillation and can be calculated using the following formula. Formula Sine Wave Oscillator The example of the circuit was made this time is shown below. f = 1 / (2 x 3.14 x 10 -6 0.01 x 10 x 15 x 3) f = 1 / (0.942 x 10 -3) f = 1.062 x 10 3 f = 1062 Hz The actual frequency of the circuit was 900 Hz.