An active full-wave rectifier using LM-741

Electronic circuits are broadly classified into 2 categories - Active and Passive.

Every analog circuitry from Differentiators to Rectifiers has its active and passive counterparts. Active circuits are composed of special components which consume electricity to function properly whereas passive circuits are those which do not need an external power source to function. Active components which are commonly used include Op-Amps, SCR (Silicon-Controlled Rectifier), etc. whereas, R, L, and C are passive components.

Let's try to visualize a passive Integrator circuit -

The transfer function or the ratio between the output and input of this circuit is given by -

Hence, the function is of the form of 1/s at very high frequencies if s is the complex frequency in the Laplace domain. Thus, some sort of Integrating action is performed but one of the main drawbacks is that the operation is frequency-dependent and integrates only at high frequencies. To counter this effect of frequency, we use an active integrator.

One of the key advantages of using this circuit is that the frequency dependency is reduced significantly and the function is integrated more cleanly.

With this brief intuition about the active and passive components, let's dive into our project. We have tried to implement an active full-wave rectifier using Op-Amp.

Circuit Diagram -

Working Principle -

The circuit employs the technique of inverting amplifiers in negative feedback to rectify a given AC signal. However, there is a phase shift of 180 degrees after passing through one Op-Amp and hence, 2 Op-Amps are used to ensure that, the output is in-phase with the input.

Output Waveform -

Word of Caution - Due to the presence of DC offset and non-idealities, the rectification option may not be so obvious for all frequencies. Try to change the frequency according to your requirements and observe the action.

Link to view and simulate the Project - https://www.tinkercad.com/things/hoI9h50dXJy-simulation1