linear1 forums
[part of the linear1 network]
+ [linear1 case mods]
+ [LED Center]
+ [privacy policy]
Welcome, Guest. Please login or register.
March 18, 2010, 03:21:43 PM

Login with username, password and session length
Search:     Advanced search
* Home Help Search Login Register

linear1 forums  |  LED discussion  |  Electronics discussion  |  Topic: the default setting of the TTL ot LSTTL Nand gate(DM74LS00) « previous next »
Pages: [1] Print
Author Topic: the default setting of the TTL ot LSTTL Nand gate(DM74LS00)  (Read 774 times)
tfcsam
Strong like bull
*
Offline Offline

Posts: 3
« on: January 29, 2008, 09:59:20 PM »
why the input level will be treated as high if there is no connection made to corresponding pin?
Logged
Rob
LED guy
Administrator
Smart like tractor
*****
Offline Offline

Posts: 1970


The constant-current gardener


WWW
« Reply #1 on: January 30, 2008, 01:09:43 AM »
As I recall, it was to save power. You'll find just about all those ICs will float inputs high (but you should never count on it).

And Welcome to the boards.
Logged
cadstarsucks
Smart like tractor
****
Offline Offline

Posts: 449
« Reply #2 on: January 30, 2008, 06:56:20 AM »
Quote from: tfcsam on January 29, 2008, 09:59:20 PM
why the input level will be treated as high if there is no connection made to corresponding pin?
I know that has to do with the internal IC structure but do not remember specifics.  That said you should always tie off pins as once you transition from TTL to CMOS (as you are likely to to save power or because it is getting harder to get TTL) you must tie them high to prevent the high impedance inputs from responding to noise and static.

Dan
Logged
Pages: [1] Print 
linear1 forums  |  LED discussion  |  Electronics discussion  |  Topic: the default setting of the TTL ot LSTTL Nand gate(DM74LS00) « previous next »
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.7 | SMF © 2006-2008, Simple Machines LLC Valid XHTML 1.0! Valid CSS!
Page created in 0.145 seconds with 19 queries.