The Philips Semiconductors 74F “Light Load” product line is a high
performance, TTL bus compatible series of very low input bias
current (±20mA), buffer/driver, transceiver, register, multiplexer and
arithmetic MSI functions. The patented “Light Load”, ±20mA NPN
input structure, shown in Figure 1, combined with a unique input
speed-up circuit (also patented) makes this product line ideal for
interfacing with all MOS devices, without any speed degradation.
When compared to the IIL of standard FAST inputs of 600mA (larger
for some other logic families) this “Light Load” input shows a
30:1 reduction in IIL loading (600mA/20mA).
These devices were specifically designed to meet the requirements
of buffering low output drive MOS VLSI/LSI devices from the
rigorous loading environment PC board/motherboard buses and
system backplanes. The “Light Load” inputs and improved speed
performance make this product line ideal for interfacing to low output
drive capability, slower MOS CPU, peripherals and semi-custom
chips used in most state-of-the-art logic designs today. Using these
“Light Load” input bus products, MOS chip outputs will only have to
drive the small amount of distributed PC trace capacitance and
inductance loading. The MOS device output drive capability is not
wasted on drivers/transceivers with large DC input current drive
requirements.
See Table 1 for a complete listing of the part numbers and functions
of the “Light Load” product line.