I've been designing a circuit using CD40xxB logic, the low speed stuff that works with a supply voltage from 3 to 18 volts. According to the CD4011B quad 2-input NAND gate datasheets from both Texas Instruments and Fairchild, when operating on a 5 volt supply, the output drive—both source and sink—is 0.51 mA minimum, and typical is 1 mA (Texas Instruments) or 0.88 mA (Fairchild). But curiously, I'm finding that they can source and sink 8 mA per gate. This is way beyond what the datasheet says they are capable of. I've tried several different ICs, from several manufacturers, and they all behave the same way. So, it seems that the datasheet is ridiculously conservative in the drive ratings.
Looking at the datasheets, they have a rough photocopied look to them, suggesting that they are the originals that date back to when CMOS was first introduced. I'm wondering if, over the years, changes in the fabrication process have improved the chips significantly. But if so, why wouldn't they revise the datasheets?
Looking at the datasheets, they have a rough photocopied look to them, suggesting that they are the originals that date back to when CMOS was first introduced. I'm wondering if, over the years, changes in the fabrication process have improved the chips significantly. But if so, why wouldn't they revise the datasheets?