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I'm trying to implement an LED driver and I found the next circuit in PSoC's Guide on how to use the GPIOs.

Thing is I don't get if it's a must to include the R3 resistor and the Q2 transistor or if it's enough configuring the Pin_4 as Strong Drive??

thanks!!

enter image description here

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If the R_2 value is large enough that it limits the current through the LED to a value that is within spec for the GPIO on the MCU and the VDD powering the LED is the same voltage level as the MCU GPIO power rail then you can directly drive the LED R_2 from the GPIO pin.

You would need the transistor and the R_3 resistor if:

  1. The LED power rail is a higher voltage than the MCU GPIO power rail such as 9V, 12V etc.
  2. The LED needs much higher current through it to illuminate it to the brightness desired.
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