power consumption of SN7407 and SN74LVC8T245

Mark,

The maximum power consumption is typically not specified in logic datasheets because it depends on a variety of factors including frequency, ambient temperature, number of loads and load current.

The following application notes can help explain further:

• CMOS Power and CPD Calculation (www.ti.com/lit/an/scaa035b/scaa035b.pdf)
• Designing With Logic (Rev. C)
• Understanding and Interpreting Standard-Logic Data Sheets (Rev. B)

That being said, the SN7404 states a typical power consumption value of 145 mW in the description on the datasheet. However, I do not know how this was determined.