## Tuesday, April 21, 2015

### Circuit Schematic Linear DC Signal Opto Insulator using LM358 IC

Eltronicschool. - Here is one of the tested circuit schematic that will useful to you to help when do measurement. This circuit is Circuit Schematic Linear DC Signal Opto Insulator using LM358 IC like in figure 1 below. As the name of the title that the based component in this circuit is LM358 IC with sheet data here.

Circuit Schematic

Description

Circuit schematic like in figure 1 above is Circuit Schematic Linear DC Signal Opto Insulator using LM358 ICThis simple circuit provides better than 1% accuracy in optically coupling a DC voltage signal. To compensate for the non-linearity of the optical insulator, an identical device is connected in the feedback loop. To further enhance stability, both optical insulators are located inside the same IC. Both the input and output circuits operate from single power supplies (one for the input side and a 2nd for the output side). Prior art generally requires both positive and negative power supplies –elimination of the negative power supplies simplifies the circuit.

A positive signal input causes the output of U1 to shift positive. This causes both LEDs to conduct. U3-B turns on and provides a positive going feedback signal. When both op amp inputs are equal, the output of U1 stops integrating. At the same time the output of U3A presents a positive going signal to U2. Adjusting R2 so that R1 + R2 »4.7K causes the output of U2 to come close to the input voltage signal –further adjustment of R2 will trim for the difference in CTR so that the output voltage will exactly match the input voltage. The easiest way to test performance is to connect a DVM between input and output.

Potentiometer R4 accommodates gross variations in the CTR (both devices). R4 is adjusted so that it drops about 2V at maximum signal level –this is very non-critical. C1 is a compensation capacitor –for faster performance, this may be adjusted down –if too low, the circuit may oscillate. I did not test the response time.

Source:
• http://www.electroschematics.com/11475/linear-dc-signal-opto-isolator/

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