[1] : The Free On-line Dictionary of Computing (27 SEP 03)

transistor-transistor logic
     
        ttl a common semiconductor technology for building discrete
        digital logic integrated circuits.  it originated from texas
        instruments in 1965.
     
        there have been several series of ttl logic:
     
         7400:	10 ns propagation time, 10 mw/gate power consumption,
        	obsolete;
     
         74l00:	low power: higher resistances, less dissipation
        	1 mw, longer propagation time 30 ns;
     
         74h00: high power: lower resistances, more dissipation: less
        	sensitivity for noise;
     
         74s00: schottky-clamped: faster switching 3 ns, 19 mw by
        	using schottky diodes to prevent the transistors from
        	saturation;
     
         74ls00: low power, schottky-clamped 10 ns, 2 mw;
     
         74as00: advanced schottky: faster switching, less
        	 dissipation, 1.5 ns, 10 mw;
     
         74als00: advanced low power schottky 4 ns, 1.3 mw.
     
        for each 74xxx family there is a corresponding 54xxx family.
        the 74 series are specified for operation at 0 - 70 c whereas
        the 54 military series can operate at -55 - 125 c
     
        see also cmos, ecl.
     
     
see also:
texas instruments cmos ecl 

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