Elenco Understanding Logic Gates - Manual (Page 8)

NOT Gate (Inverter)
A Q
Input (A) Output (Q)
0 1
1 0
U15
1
0
NOT gates are used in digital logic circuits to “invert a voltage level”. A high voltage level (1)
into the NOT gate becomes a low voltage level (0) at the output and vice versa.
1
1
1
1
2
2 2
2
2
2
Place parts labeled 1 on the grid
first and parts labeled 2 on second
Note: High electric currents can damage LEDs, so normally resistors
are placed in series with LEDs to protect them. Resistors aren’t
needed with your Snap Circuits® D1 & D2 LEDs, because they
already have internal resistors to protect them from incorrect
wiring.
External resistors would be needed with the LEDs if you
were using your logic gates (U15-U20) to control other logic gates
along with the LEDs, because the low resistance of the LED and its
protection resistor could disrupt the operation of the logic gates
being controlled.
This circuit demonstrates how the NOT
Gate (U15) works. Connect one end of
the red jumper wire to the A input on
U15 and the loose end to either low
voltage (denoted as a “0”) or high
voltage (denoted as a “1”). If input A is
low (0, green LED off), then the Q output
on U15 will be high (1), and the red LED
(D1) will be on.
The inversion of a state is often
represented
with a bar over the
variable, so Q = A .