Alt-BEAM Archive

Message #12775



To: alt-beam@egroups.com, BEAM beam@sgiblab.sgi.com
From: David Simmons devs@idirect.com
Date: Wed, 29 Mar 2000 21:54:04 -0800
Subject: [alt-beam] RE:A biocore question??


Below as posted by Dane Gardner last month.

Sure, here's my notes for a test I had a couple of semesters ago.

74 (usually) means that it is a commercial chip. As opposed to the
military 54 series. The 54's are WAY more expensive and are not worth
it. The difference? The military chips have a broader power rating,
they can handle extreme temperatures (high and low), and aren't supposed
to be as static sensative as the 74's. Then there's the old 4000 series
that is just a low speed CMOS. And the BiCMOS that combines CMOS and
TTL
(not comatabilities, but actual technology within the chip
itself).

There are a whole bunch of other chip styles...but I've only run accross
them once or twice in ten years now, so don't worry to much about them.

The real difference between CMOS and TTL is in performance. Like
propagation
delay (switching speed), noise immunity, power disipation, static
sensativity,
etc. A lot of the more advanced TTL is faster, but SUCKS down the power
(the S series wasn't even worth it unless it was plugged into a
wall). In these notes, I generally went from oldest to newest tech,
which
usually means that its slow to fastest.

Complementary Metal-Oxide Semiconductor (CMOS) circuits are generally
implemented
with a type of Field-Effect Transistor. Some of their flavors are as
follows:

5V Series:
HC -- High speed CMOS
HCT -- High speed CMOS with TTL compatability
AC -- Advanced CMOS
ACT -- Advanced CMOS with TTL compatability
AHC -- Advanced High speed CMOS
AHCT -- Advanced High speed CMOS with TTL compatability

3.3V Series:
LV -- Low Voltage CMOS
LVC -- Low Voltage CMOS (same as above, just a next generation)
ALVC -- Advanced Low Voltage CMOS

BiCMOS:
BCT -- BiCMOS
ABT -- Advanced BiCMOS
LVT -- Low Voltage BiCMOS
ALB -- Advanced Low Voltage BiCMOS

Transistor-Transistor Logic (TTL) is implemented with bipolar junction
transistors. Some TTL series
packages:

74 or 54 no letters -- straight TTL
S -- Schottky TTL
AS -- Advanced Schottky TTL
LS -- Low power Schottky TTL
ALS -- Advanced Low power Schottky TTL
F -- Fast TTL
Cory Houck wrote:
>
> can you use a 74hc240 and 245 instead of 74HCT240 and 245??????
> and what is the big difference with the middle numbers.
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