My teacher asked me to explain the reason why we need to tune the offset of the function generator of a ttl circuit to 2.5v(or -2.5v::didn't hear it clearly!) to create a shift from -2.5v to 2.5v instead of having it shift between 0v to 5v. I've done some research regarding the high voltage and the low voltage of a ttl circuit, saying that most ttl circuit have a low voltage between 0~0.8v and a high circuit between 2.35v~2.5v, is that reason why we need to tone down(or bump up) the offset?? The question is in the following: In TTL digital circuits, the “clock” signal like the left-handed picture below is frequently needed. However, the waveform output from F.G. is like the right-handed picture. How do we make the output waveform from F.G. be acceptable by TTL circuits? can anybody help me explain the reason also tell me if the offset is to be bump up or tone down, in MHO I would say the offset needs to be tone down to -2.5v, but somehow I heard my teacher said 2.5v.