Brief AND Gate using NPN BJTs Bipolar Junction Transistors

Making an AND logic gate with Bipolar Junction Transistors (BJTs) is a good way to practice building circuits.

Simple AND logic gate using NPN bipolar junction transistors BJTs schematic diagram by electronzap aka electronzapdotcom
Simple AND logic gate using NPN bipolar junction transistors BJTs schematic diagram by electronzap aka electronzapdotcom

Current has to flow through both collector to emitters in order for the output to get power. When that happens, the output is considered on, or high.

If either transistor is off, then there will be no current flow.  Same if both are off. Therefore the output will be off if any, or all, of the transistors are off.

If only input B is closed, then close to 0.5 volts will build up at the output due to the emitter resistor. It is acting as the lower part of a voltage divider.


Nice assortments of semiconductors that I use in my videos. Includes 2N3904 NPN BJTs and 2N3906 PNP BJTs. Amazon affiliate link ad.

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Brief Circuit Schematics with Short Video List of Pages

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