If there were a 4000-series 7-segment decoder (with outputs like a 4026/4033) then it could probably be used without resistors, for a small range of supply voltages.

For a home project, maybe. But in my experience, that approach would not even make it into a design review.

In my less-than-glorious past I have occasionally abused a CMOS output stage by relying on it for both self- and load-protection. But these days, parts are so cheap that why bother? It is more work to work out if it is safe to eliminate the resistors than to just put them in.

ak

 

LED's require a current limiting resistor. Which keeps being incorrectly refered to as ballast.

LEDs, 555s, Flashers, and Light Chasers

 

Still waiting for a link to the source of the quote in post #1. It might be that it was a bad suggestion that was rejected (and explained) in the thread by multiple people.

ak

 

For a home project, maybe. But in my experience, that approach would not even make it into a design review.

In my less-than-glorious past I have occasionally abused a CMOS output stage by relying on it for both self- and load-protection. But these days, parts are so cheap that why bother? It is more work to work out if it is safe to eliminate the resistors than to just put them in.

ak

These days, It would probably have a microprocessor, and I'd use something like a TLC5952 which has constant current outputs set by a single resistor.

 

Well, that didn't take long. Relative?