Brief NPN BJT timed off fade circuit- RC time constant

Table of Contents

Capacitors take time to discharge through resistance, but they do not store enough energy to power a load.

2N3904 NPN BJT pin layout schematic symbol and current paths diagram by electronzap electronzapdotcom
2N3904 NPN BJT pin layout schematic symbol and current paths diagram by electronzap electronzapdotcom

A small amount of capacitor discharge current flowing through the base to emitter of a bipolar junction transistor translates into a lot of current flowing through the collector and emitter of the transistor. That current also flows though any load on the collector side of the circuit. At some point the capacitor will run out of current that it can provide and the transistor will turn off over a period of time.

The 2N3904 is very popular NPN Bipolar Junction Transistor (BJT).

The pin layout and direction of voltage and conventional current flow (positive to negative) is shown in the first diagram.

Diagram

Simple NPN BJT RC time constant fade off switch circuit schematic diagram by electronzap electronzapdotcom
Simple NPN BJT RC time constant fade off switch circuit schematic diagram by electronzap electronzapdotcom

Amazon affiliate ad. Learned a lot from this book.

Video

Quick timed fade off NPN BJT switch circuit using 2N3904 bipolar junction transistor by electronzap



A lot of the components that I use are in this diode and transistor semiconductor kit.

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