Is it possible to make a Tri-State Bidirectional buffer without any tri-state buffers?
A tristate inverter has truth table:

enable, in, out
0, 0, z
0, 1, z
1, 0, 1
1, 1, 0


You can build such a thing with CMOS transistors. The pull up network has two PMOS in series, and ther pull down network has two NMOS in series. In connects to the lower NMOS and the higher PMOS, and the complement of enable goes to the other two transistors.  That looks like this:







simulate this circuit &ndash; Schematic created using CircuitLab

You can build other variations on this by introducing inverters in various ways.