Hello to everyone,
because the 7408 IC evaluate a not connected pin as HIGH, I need to supply a LOW value when a ON/OFF switch is turned off in order to receive a LOW output from my AND gate...
So, the simple example is shown in the image attached: how to supply the 7408 a LOW value when no input is given?
Attach a resistor (10k, 1K, anything in between will work) from each input to Gnd.
Look into pull up resistors and pull down resistors.
[quote author=Runaway Pancake link=msg=2245262 date=1432422417]
Attach a resistor (10k, 1K, anything in between will work) from each input to Gnd.
[/quote]That resistor range will only work if it's a CMOS version of the 7408. As the OP has written "the 7408 IC evaluate a not connected pin as HIGH", I wonder if it's a TTL chip.
If you are sure the switches are break-before-make, you can put the switches the other way around so you simply switch 0 volts or 5 volts to the inputs (if TTL, you only need to switch input to 0 volts).
Wire the switch so that you switch the inputs to ground not 5V. If it is a TTL gate it floats high naturally but add a 10K pull up resistor for better noise immunity.
