LED Driver with Single NPN Transistor

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This driver is able to drive LEDs by applying a high logic level sourced from output pin of a logic IC belonging to common 74xx logic families (HC, HCT, LS, etc.) or CMOS microcontrollers.

The output pin of IC is simulated by a voltage supply and a switch.

General rule of thumb is that the output pin of the IC has to be able to source at least 1 mA of current when it is set to high logic level.

As a real NPN transistor, you can use almost any "jellybean" small-signal one, such as BC54x or 2N3904, which are cheap and widely available.

published 6 years ago

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