Vcc-2 referring to in the Texas Instruments Tech Sheet for the SN74AS138


Total noob here.

The tech sheet can be found here:

In the VOH parameter for the SN74AS138 on page 5, it states that it's MIN is VCC-2.

What does that mean? What is referring to? Is it referring to the actual VCC minus 2 volts? So 2.5V for VCC = 4.5V?

Here's the snippet I'm talking about:

Snippet from datasheet

Best Answer

It is a simple sum.

It refers to the output voltage when an output is HIGH (\$V_{OH}\$) as a minimum (it's in the MIN column) of 2 volts below \$V_{CC}\$, so if \$V_{CC} = 5V\$ then \$V_{OH}\$ will be at least 3V.

For CMOS you will often see something like \$0.6V_{CC}\$, where the value is 60% of the \$V_{CC}\$ value.