2025 Component Abuse: Digital Logic With Analog Parts
▼ Summary
– [Tim] observed that many discrete logic projects use outdated 70-year-old technologies like RTL or DTL, which are hard and expensive to source today.
– He invented a new logic system using analog multiplexers for the Component Abuse Challenge instead of relying on antique components.
– Analog multiplexers can pass analog signals because their transistors don’t saturate, unlike digital multiplexers that only handle 1s and 0s.
– His initial design had a polarity error that caused latches to oscillate, but a second simplified version with fewer components worked successfully.
– The second prototype operates at 15 MHz and has potential for even higher clock speeds in future designs.
Building digital logic circuits with modern analog components offers a fresh approach for electronics enthusiasts tired of hunting for obsolete parts. Rather than relying on hard-to-find resistor-transistor logic or diode-transistor logic components, one innovator has developed a functional logic system using analog multiplexers. These versatile chips, typically employed for routing analog signals, form the foundation for an entire family of logic gates that operate without depending on vintage semiconductors.
Analog multiplexers differ from their digital counterparts in their ability to handle continuous voltage ranges rather than just binary states. This characteristic makes them ideal for creating logic circuits that function reliably without pushing transistors into saturation. The system demonstrates remarkable flexibility, with more complex elements like latches becoming possible through strategic incorporation of capacitors. This approach transforms ordinary analog components into fully functional digital building blocks.
The development process wasn’t without its challenges. An initial implementation encountered unexpected behavior when latches began oscillating instead of maintaining stable states. This turned out to result from a simple polarity reversal in the circuit design. After identifying and correcting this issue, a refined version emerged with both simplified architecture and fewer components. This second iteration not functioned correctly but achieved impressive performance at 15 MHz clock speeds.
What makes this achievement particularly noteworthy is the potential for even higher operating frequencies in future implementations. The success demonstrates how unconventional thinking with common components can yield practical solutions that rival traditional approaches. This method opens up new possibilities for circuit designers seeking alternatives to conventional digital logic families while maintaining competitive performance characteristics.
(Source: Hackaday)
