ECL primer

As a followup to the observation Siuki makes about finding the reference for
a CMOS driver, beware, because you will get to Vth, the threshold voltage of
the driver transistor that is on, of the reference voltage and the transistor
will turn off. You cannot make assumptions about the magnitude of the
threshold voltage as some manufactures back bias the transistors for any
number of reassons, which results in shifting the threshold voltage, sometimes
quite a lot. So unless you are privy to this circuit detail, you will have
an unknown error in this measurement. Even if you know that back bias is
present, and if you knew how much, you still can't determine the Vth shift
without process details, say from a Spice model.

Sincerely,

Bob Ward
Received on Mon Sep 13 11:35:13 1993