# Understanding circuit diagram on datasheet and resistor value

Posted on Feb 4, 2014

Interested in starting an intro electronics project using a IR sensor and am having a little trouble understand the application circuit given on the datasheet of the circuit. The value of resistor they recommend using is far less then the one I calculate I should need. The supply current given on the datasheet is 0. 27mA - 0. 45mA and the suppl

y voltage is 2. 5V - 5. 5V. I intend to run this sensor at 0. 35mA with 3. 3V and this yields a needed resistance of around 10K ohms; far greater than the 33 - 1K ohms suggested. As this is my first venture into electronics, could someone help me to understand how using such a low resistor as specified would work when the math says otherwise On a slightly related note, from what I understand, the capacitor in the circuit is called a decoupling capacitor and is used to provide the extra current during short periods of high current draw so the voltage supply does not. Because this is such a low current circuit (or is 0. 35mA low ), is it fine if I leave the capacitor out or should I include it because the datasheet lists the absolute maximum current as 3mA and the circuit may try to draw that much

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