I'm trying to make a low-current level shifter from low voltage (~2V) CMOS up to 5V CMOS.

I had the idea to use TTL-compatible CMOS gates in the HCT or ACT families.

But this line in the 74HCT04 datasheet that concerns me, the "additional supply current" line. This is not in the HC version.

enter image description here

Is this a static current drain? Or only when the input is high? Or what?


HCT/ACT devices have a modified input stage that is compatible with TTL levels, but is still composed of MOSFETs. Since these MOSFETs will be in their ohmic region with a TTL high, there will be a high-resistance path from VCC to GND. The "additional supply current" represents this extra drain when the TTL high (specifically VCC-2.1V in this case) is presented to the input.


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