[TTL inverters]

hai,
thie reason for showing a transistor is exactly that the other guy has said.It is because , in manufacturing, they dont bother to make two independent diodes connected back to back.Keep in mind that the diodes themselves are made from transistors in wafer.So, why should they use two transistors to make a pair of back to back connected diodes when they can reasile the same effect with just one transistor!!!
Well, some documents show it as two seperate diodes and not as transistor because the authors of the document wants to make the reader aware that the functionality is just that of two diodes and not that of the transistor.Hope you understand the probelem.Even you where confused about why the transistor is not biased, because you have a prejudice that all transistor should work in actie region or something like that.Well, actually they can be used as diodes also.

nishi

[Unknow current in transformer]

common MP,
What the other guy has been telling is correct.Transformer winding ratio has nothing to do with the resistance values of either winding.Their is no way to findout the ratio other than actually applying a frequency sweep to the primary and plotting the amplitude at secondary.Well..., may be i dont know another method.

nishi