The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with the positive direction of the current and vice versa. So, is it possible to change the waveform to the modulus of a sine wave? And if so, with what?

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    \$\begingroup\$ Diode rectifier. \$\endgroup\$
    – DKNguyen
    Nov 19, 2022 at 6:56
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    \$\begingroup\$ Within simulators, abs(sin(x)) ... \$\endgroup\$
    – Antonio51
    Nov 19, 2022 at 7:44

2 Answers 2


A bridge rectifier will make that conversion, with a bit of voltage loss (two diode drops).


simulate this circuit – Schematic created using CircuitLab

enter image description here


This circuit is called a dropless full-wave rectifier, absolute-value circuit or super-diode. The function of it is to perform full-wave rectification without the diode drops that occur in a "normal" full-wave rectifier.


When the input swings negative, the anode of D2 remains at 0 V and IC2 performs unity gain inversion. When the input swings positive, IC1 acts as a unity gain inverter and because of the weightings of IC2's input resistors, twice the negative value of Vin is added to Vin and inverted by IC2 to produce an output equal to Vin.

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    \$\begingroup\$ To explain better: when the goal is to transfer power (AC to DC conversion), we would use the diode bridge because it is simple and can handle lots of power. When the goal is signal processing, we could use something more like this circuit because it is more precise. \$\endgroup\$
    – user253751
    Nov 19, 2022 at 8:48
  • \$\begingroup\$ @user253751 Yes, exactly right. \$\endgroup\$
    – user173271
    Nov 19, 2022 at 9:02

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