I have studied the data sheets on both of these chips and cannot figure out which one is best for driving common cathode displays. If some of you have read my other posts you will understand that I don't want to make the same mistakes. Like I did when I bought common anode displays and I had a common cathode driver. lol. Any suggestions?

 

The 7448 is designed to drive common cathode circuits, while the 7447 is designed to drive common anode circuits. You can use a 4511 and it will drive either depending upon its set up.

 

How do you set the 4511 to drive anode?

Thanks for the info on the other chips. Very useful.

 

Take a look at the 4543, also. See your other thread; I added a schematic and some notes.

 

You need inverting transistors to handle a common anode display - the 4511 is designed for common cathode.

You should be aware that a 4000 series CMOS IC and old TTL (74XX) do not play well together. Specifically, the TTL HIGH level is not enough to switch the input of a CMOS gate. Life is easier if you use the same logic family throughout a project.

 

You need inverting transistors to handle a common anode display - the 4511 is designed for common cathode.

You should be aware that a 4000 series CMOS IC and old TTL (74XX) do not play well together. Specifically, the TTL HIGH level is not enough to switch the input of a CMOS gate. Life is easier if you use the same logic family throughout a project.

For learning purposes I ended up using the two together. See my learning adventure here: http://forum.allaboutcircuits.com/showthread.php?t=35657

My actual project will be all TTL. I am using common cathode displays. k7elp60 posted that the 7448 is the one designed to drive them.

I was curious of the 4511 because that is what I have now for my experiments. I can't, however, drive the dual anode displays because of their circuitry. I want to convert the 4511 so they could, and then hopefully learn to drive the anode displays. Thread here: http://forum.allaboutcircuits.com/showthread.php?t=36149

 

You need inverting transistors to handle a common anode display - the 4511 is designed for common cathode.

You should be aware that a 4000 series CMOS IC and old TTL (74XX) do not play well together. Specifically, the TTL HIGH level is not enough to switch the input of a CMOS gate. Life is easier if you use the same logic family throughout a project.

My impression about CMOS (something I was rather sure of actually) is anything over ½Vcc is a high, and anything under ½Vcc is a low. I've successfully mixed them, but it has been measured in decades. TTL high is around 3.4V last I checked.

 

It does look almost a sloppy as TTL in the manual - 1.5 volts low and 3.5 volts high. My experience is that it's not that forgiving, and really likes highs closer to the Vcc level.

 

I was wrong, the 4511 is for common cathode displays. I was thinking 4543. The 4543 is good as it will also drive LCD displays. The Ph pin(6) is at ground or Vss for common cathode or Vdd for common anode, the for LCD pin 6 is connected to a oscillator.