Experiment 12 - The NOT Circuit
The simplest logic operation is the NOT logic.
The corresponding logic unit has only one input and one output.
That you can easily replace it with a transistor circuit.
The truth table shows you the NOT-logic.
The result at the output Q
negates the input
Truth Table of the NOT logic.
NOT symbol in circuit diagrams.
Transistor circuit of a NOT logic unit.
Circuit diagram of NOT logic with a transistor.
Now you replace the integrated circuit (IC)
from the last experiment by the transistor circuit shown.
When the pushbutton switch is open
(A = 0),
the transistor is blocked and current flows through the resistor R2a
The LED lights up
(Q = 1).
When you press the pushbutton switch
(A = 1),
the transistor switches through and hence shortcircuits
The LED goes dark
(Q = 0).
This is the logical behavior of a NOT unit.