These transistors may come with straight or preformed leads.If you need a little beefier PNP transistor, look at our PN2907 which can support up to 800mA. Using two 100 ohm 1/4W resistors in parallel would be another approach. Power through the that resistor is P = 60mA * 3V = 180mW so a 1/4W resistor will work, though a 1/2W would be a better choice for long-term use. The example assumes an LED voltage drop of 2V, so R = (5V – Vled) / 60mA = 50 ohms. This value may vary a bit depending on what LEDs are being used. The 50 ohm resistor sets the overall current for the 3 LEDs. The 4.7K resistor on the base is there to limit the current out of the uC pin to safe levels and the value is not overly critical. This simple circuit allows you to drive all three LEDs off the same uC pin. You could use 3 pins on the uC to drive the 3 LEDs, but that is a waste of pins unless you have pins to spare. The indicator consists of 3 LEDs which each draw 20mA of current.Ī uC pin can easily drive an LED at 20mA, but this will require 60mA which is outside the range of the typical uC drive capability. We have an LED indicator that we want to drive. PNP transistors are generally used in high-side switching applications where they are connected between the load and power. 2N3906 BJT PNP Transistor TO-92 product reasonable price, fast shipping options with 2N Transistors category online at Turkeys largest electronic component. These can be very handy when you need to boost the output of a uC pin to drive something that it can not drive directly. The 2N3906 are a good inexpensive general purpose PNP transistor for low power amplification and switching and should be part of every parts bin.
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