Final answer:
A NOT gate can be constructed using one transistor and a resistor, where the transistor operates as a switch to invert the input signal.
Step-by-step explanation:
True: A NOT gate, also known as an inverter, can indeed be constructed from one transistor and a resistor. The basic concept is that the transistor can act as a switch. When voltage is applied to its base, it allows current to flow from the collector to the emitter.
If we consider a digital logic level, with a high voltage representing a logical '1' and a low voltage representing a logical '0', when the input to the transistor (connected to the base) is at a high voltage (1), the transistor conducts and pulls the output voltage (connected to the collector through a resistor to the power supply) down to a low voltage (0).
Conversely, when the input is low (0), the transistor does not conduct, and the resistor pulls up the output voltage to high (1). Therefore, the output is the inverse of the input, which is the function of a NOT gate.