Initially, the 4000 series was slower than the popular 7400 TTL chips, but
had the advantage of much lower
power consumption, the ability to operate over a much wider range of supply
voltages (3V
to 15V), and simpler
circuit design due to the vastly increased
fanout. However
their slower speed (initially only capable of about 1
MHz
operation, compared with TTL's 10 MHz) meant that their applications were
limited to static or slow speed designs. Later, new fabrication technology
largely overcame the speed problems, while retaining backward compatibility with
most circuit designs. Although all semiconductors can be damaged by
electrostatic discharge, the high impedance of CMOS inputs made them more
susceptible than bipolar, TTL, devices. Eventually, the advantages of CMOS
(especially the later series such as 74HC) edged out the older TTL chips, but at
the same time ever increasing
LSI techniques edged out the modular chip approach to design. The 4000
series is still widely available, but perhaps less important than it was two
decades ago.
CMOS4000