Digital logic, an Inverter or NOT gate Digital logic, an Inverter or NOT gate | Page 12

Concept about NOT GATE :-
It is a single input device which has an output level that is normally at logic
level “1” and goes “LOW” to a logic level “0” when its single input is at logic
level “1”, in other words it “inverts” (complements) its input signal. The
output from a NOT gate only returns “HIGH” again when its input is at logic
level “0” giving us the Boolean expression of: A = Q.
Then we can define the operation of a single input digital logic NOT gate as
being:
“If A is NOT true, then Q is true”
TRANSISTOR NOT GATE –
A simple 2-input logic NOT gate can be constructed using a RTL Resistor-
transistor switches as shown below with the input connected directly to the
transistor base. The transistor must be saturated “ON” for an inverted
output “OFF” at Q.