10Pcs Transistor NPN 2N3904

Description

The 2N3904 are a good general purpose NPN transistor for low power amplification and switching.

Qty 5 ? 2N3904 NPN General Purpose TransistorsNPN Bipolar Silicon construction

Standard EBC pin-out in TO-92 package

Up to 40V collector-emitter and 60V collector-base

Up to 200mA current

100MHz switching speedThe 2N3904 are a good inexpensive general purpose NPN transistor for low power amplification and switching and should be part of every parts bin.

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.? NPN transistors are generally used in low-side switching applications where they are connected between the load and ground.

Here is a simple example circuit.? We have an LED indicator that we want to drive.? The indicator consists of 3 LEDs which each draw 20mA of current.

A uC pin can easily drive an LED at 20mA, but this circuit will require 60mA which is outside the range of the typical uC drive capability.? 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.? This simple circuit allows you to drive all three LEDs off the same uC pin.