Finding electronic circuit diagrams/schematics is fun if you’re doing an electronic building as a hobby. Learning already made circuit schematic diagram is a good start to design our own circuit. Sometimes we think that designing our own circuit is smart, showing to people that we capable to design our original circuits. If you insist that you have really original circuit that you design yourself, then you would be disappointed when someone show you that many others have designed similar or even same circuits with yours. It happens because you share the same theory with other electronic engineers, and to be honest, many designers practically implement their design by combining functional blocks they have learned in other circuits. For the extreme examples, you can’t avoid using voltage divider, zener diode voltage regulation, decouple capacitor, bridge rectifier, emitter follower, zero crossing detector, inverting op-amp amplification, and many other basic circuit elements that you have learned from our books and other collective knowledge of implemented circuits.

It is stupid to design your own circuit if there is already designed similar circuits. The smarter decision is to search already made design, improve it, or modify to suit your need. Then it is wise to share the modification/improvement by publishing it in a public media, so others can avoid a stupid things by trying to redo what you did. Only if you couldn’t find your needed circuit then it’s the time to design by yourself. Still, it’s better to share your original design to help others that need same or similar circuit functionality.

Here we present many circuit diagrams/schematics that have been published in public domains, so you can free to use it, modify, or improve it. We will give credits to the original authors of the circuits if they’re known. Enjoy it.