Delete comment from: Ken Shirriff's blog
When I was in engineering school in the 1970s, I worked at a security alarm company. Our products used 4000 series CMOS chips. In those days, they functioned a lot like 74XX TTL chips, but were slower and required a lot less power. One could use a couple of resistors on an inverter to create a crude op-amp, or select between analog signals using a mux, there were all kinds of design tricks used with these chips. Also, the supply voltage ranged from 3 to 15 or 18 volts, so pretty much anything could supply power to these chips, as long as it was filtered. Some of our system used power stolen from other sources, like a 20 mA current loop, so there wasn't even a battery or power cord.
Jan 28, 2024, 2:43:36 PM
Posted to Reverse engineering CMOS, illustrated with a vintage Soviet counter chip