
3.6 AND AND OR OPERATORS AND THEIR MIXED-LOGIC CIRCUIT SYMBOLOGY 87
on the output of an inverting tri-state driver in the transfer mode indicates an inverted voltage
signal. Thus, if X is at LV, then
¯
X is at HV and vice versa.
Buffers, or line drivers as they are sometimes called, may be composed of a series of
inverters or gates used as inverters, or they may be simply a tri-state driver operated in the
transfer mode. Remember, it is the function of a line driver to boost and sharpen signals that
might otherwise degrade below switching levels or be distorted. The mixed logic circuit
symbols for buffers are given in Fig. 3.20a.
3.6 AND AND OR OPERA ...