All About Circuits

74LS08 troubleshooting (weird output) NOOB WARNING

Search Forums New Posts
takao21203

takao21203

Joined Apr 28, 2012
3,702
MrChips said:
You have at least three mistakes in your setup. There are more when you get into the details.

As pointed out already:

1) You need pull-up or pull-down resistors on the switches. You have to get the values correct.
2) You need a resistor in series with the LED.
3) You have to be aware the two ways of connecting the LED, as current load or as a current source.
Click to expand...
2) All TTL limit the current to an equivalent of 150 Ohms in reality this means LED wont burn out.
Just your output will be pulled down quite a lot.

Many modern TTL work at less than 5v tough the old kinds dont. Also many modern LEDs are fine with 1mA so indeed you should have some 2.2k to 4.7k resistors
 
You must log in or register to reply here.
Thread starter Similar threads Forum Replies Date
Chittadeepan07 I cannot find ltspice lib file for 74ls08 and 74ls107 PCB Layout , EDA & Simulations 6
1 74ls08 giving output without inputs Homework Help 5
L 74LS08 General Electronics Chat 11
D integrated circuit simulation 74LS08 General Electronics Chat 0
K 74LS08 trouble Homework Help 4
Similar threads
I cannot find ltspice lib file for 74ls08 and 74ls107
74ls08 giving output without inputs
74LS08
integrated circuit simulation 74LS08
74LS08 trouble

You May Also Like

Top