It sounds like you’re referring to the famous Elektor “305 Circuits” — likely a collection from the magazine Elektor (or its Indian edition Elektor India).
Rating: 5/5 Stars – A foundational text for the electronics hobbyist. elektor 305 circuits
Audio and Hi-Fi: From simple preamplifiers and tone controls to more complex Class-D experiments and signal processors. It sounds like you’re referring to the famous
Here is the argument for keeping the Elektor 305 in your digital library: 7-segment display decoders/drivers
Transistors: BC547/557 or 2N3904/3906 usually work as direct replacements.
Clever Engineering: Many of these circuits use "tricks" to minimize component counts. Studying how an engineer used a single hex-inverter chip to create a complex oscillator is a great way to improve your own design logic.
Published by: The DIY Lab Reading Time: 4 minutes